I'm using a RaspPi 3 but the CHIP is certainly cheaper that the PI.
Yeah, I'm cheap and had the CHIP on hand looking for something to do with it

I've never been a huge Pi fan...I want to be a fan but ... it just doesn't "fit" for anything I can think of to do with it. It's not really powerful enough to be used as a "computer" and lacks the I/O to be used like a micro. It's just kind of this halfway thing that tries to be both but fails. At least, the original Pi. The 3 seems like it may be powerful enough to be interesting...but I'm just not in a big rush to pick any up. Icee keeps trying to talk me into building one of his FlyingPi's (
https://forum.dronin.org/forum/d/20-flyingpi-advanced-flight-controller-for-robotics-machine-vision) which is one of the few applications for the Pi that seems to make some sense to me...but I'm still not convinced it actually has enough power to be worthwhile. Though it is tempting having a full linux system to work with on a FC.
So far I like OctoPrint the lack of an decent mobile app is pretty annoying, but I'm a mobile developer for my day job and I'm MAC/iOS predominatly so I'm really thinking of eventually making a iOS app.
Printoid for android is the one I'm using and am quite happy with. I like macos (though admittedly I still HATE finder and apples keyboard handling drives me up the wall...but iTerm2 with zsh freaking rocks!) but I'm not a fan of iOS. I do web development and some system administration for my day job and have dabbled in mobile development with libGDX - but never tried building for iOS since I didn't have a mac to build on at the time I was dabbling. Now I've got a mac but haven't got around to messing with mobile again. I'd dust off my
old game project...but libGDX has changed so much it would probably just be easier to start from scratch than try to update my code

My daughter still enjoys playing it sometimes though so the week of free time I spent on it was time well spent

(Side note...wow...can't believe that was 4 years ago I did that...feels like it was a lot more recent!)
I'm not sure what iOS options there are for octoprint...I was under the impression there were better options there than for android when I first tried it last year and the only android options were outdated or really clunky.
Thats really stinks. Thats pretty slimy in my opintion. I can see turning it off in new premium versions, but to turn it off in older versions is pretty lame. Just deprecate the version and drop support for it.
Yeah, really soured me on them. repetier started as an open source project but has slowly gotten more and more closed. I respect that they're trying to make a living out of it...but that kind of strong arm move is a bad way to try and influence potential customers IMHO. They did say that they were beta features only available until the release came out...but they never said that they'd take the features out of the beta when they did the release...and they didn't really do a release. Just declared the beta good enough and renamed it as a release more or less with no new features. If they had added some new functionality it would have helped soften the blow.
I was actually considering trying repetier firmware on my machine I was so happy with host/server....it looks like a pretty slick setup with much easier configuration than Marlin. But don't see myself doing that anytime soon now. I was actually getting ready to test using repetier-server to flash new versions of marlin - but that was one of the things they removed when they left beta
I did get that kind of working on octoprint with a plugin...but I've had mixed results with it and sometimes it just hangs. It isn't in the official plugin listings but there is a flashing plugin on github:
https://github.com/OctoPrint/OctoPrint-FirmwareUpdater
I've also switched from using arduino's IDE to platformIO and deviot in sublimetext for building Marlin which is quite nice since the arduino IDE has always bugged me. My only complaint is platformIO leaves the .hex file in a non-obvious place and I haven't had time to figure out how to make it copy it to a better location after compiling. One more thing on my list of things I'll probably keep putting off
I have not done anything with SSH yet with it other than SSH to the Pi directly. I know there are some plugins that will aid in linking it up with sound of the Cloud based services to allow anywhere access.
Yeah, there are a couple of different plugins for octoprint that use various cloud services. And there are things like ngrok and pagekite...but I'm not a fan of relying on a proprietary 3rd party service when there's an existing tech that already "just works" like ssh port tunneling. Though for people who don't already have an internet accessible server like my linode those are great options.
There's also the option of using dyndns or noip to just make your local network accessible...but I've never had good luck with my routers built in support for those services and don't like having to run an app on one of my computers just to keep my IP updated with them. Plus it's kind of a pain to safely and securely configure the firewall in my router going that way.
So for me using an SSH tunnel which I'm familiar with is the easiest and quickest way

But it's probably not the best bet for everyone
I have not looked at their API yet at all is it REST based?
Yes it is:
http://docs.octoprint.org/en/master/api/index.html
The problem is the way I have HAProxy configured right now is forcing htaccess authentication on the API requests...which is silly since the API has it's own key based system for security. I just pretty blindly followed the info in the octoprint wiki on how to configure HAproxy instead of taking the time to actually understand HAproxy though....I'm sure a bit of time looking at it and I can tweak the config to allow API traffic through without authentication....(like give it an exception when the X-Api-Key header is set.) I just haven't felt like putting any time into it since it's a minor annoyance.
OctoPi was a piece of cake. I essentially imaged the SD card booted and was pretty much ready to go. I've been installing some additional plugins. I need to look into their API some and figure out whats going on with that. I'd really liike a good native app for iOS. The TouchUI plugin and the Anywhere plugin are nice but I'd still like to have the ability with the app to use it as a joystick for the steppers and move it with out having to have the mac next to me.
Printoid on android has really impressed me....but....octoprint overall is a bit slow for my tastes. Even going through the web interface I find it annoying how slow the machine is to respond to inputs from the motion controls in the GUI. Commands sent directly through the console seem to work quick so I'm not sure why octoprint's GUI is so sluggish on the CHIP. The load on the CHIP is almost non-existent so I don't think it's a processing power issue. Just something about octoprint is non-optimal with how it handles some things it seems.