My son and I started with the Towel this summer and had a ball with it. We went thru three airframes before we discovered FlightTest and we haven't looked back. The towel is pretty tough and you will be amazed how long you can fly one even after severe crashes. Just add some packing tape and off you go. I also really like the coroplast module idea as it made swapping out airframes very easy.
The downside to the Towel is that is isn't the most stable aircraft and without landing gear, every landing is basically a controlled crash. Even if you are good at flying it, just a little error on landing and you will be crushing the nose or bending the wingtips. Also I ended up buying a full 50' pack of blue Fanwood foam from Lowes for ~$45 because I couldn't find any local source for a sheet or two.
Once we discovered flitetest, we built two nutballs because they were starter planes and my son thought they looked like a lot of fun. We bought recommended electronics for the swappable and went flying. Our experience is the nutball is anything but a good beginner plane. Very unstable and very susceptible to wind. We then built FT Flyers and that is when we REALLY started enjoying flying. FT Flyer is an awesome beginner plane as countless others have stated here. The flyers were the first planes we felt like we were actually flying and we were finally able to go thru entire batteries with no crashes. I've flown mine (with landing gear) easily through 20 batteries and there literally isn't a scratch on it.
So where am I going with this? I loved the Towel and am grateful it allowed my son and I to get into RC cheaply and with no fears of crashing. I am more grateful that it led me to Flitetest! So if I had to do it all over again, I would recommend starting with the FT flyer because it is simple to make and repair, cheap, stable and also will give you the electronics to move to many other FT designs.