The FlySky i6 and i6X are a great value for people on a tight budget who want a 6CH+ TX. You get all the basics you need to get started including 20 model memory, rates, expo, endpoints, subtrim, reversal, throttle curve, programmable failsafe (for the RXs that support it), built in delta/vtail mixes and 3 free mixes so you can implement differential thrust. Unfortunately the i6 (probably the i6X) does not have a way to enable/disable a mix which is a bit limiting. You also get telemetry which is only kinda useful because of the very limited alerting.
There is hack firmware available that improved the capabilities and makes the telemetry a little more useful among other things like more channels and a timer. You may want to consider ordering the FlySky data cable at the same time. I have heard it doesn't work with the i6X but I don't see why that should be...probably worth it for the parts even if you have to rewire it.
The main negatives are...
1. The gimbals are plastic bushed and will wear out fairly quickly. The springs are very small, occasionally break and can't be sourced easily. However, banggood did and probably still does sell replacement stock gimbals for the i6...probably the same for the i6X for around $8.
2. The case is smaller which you may or may not like but generally it is a bit cheesy feeling (and looking if you are vain)
3. The switches are a bit wobbly and tend to fall apart
4. AA batteries in spring frame are used to power it and that is not easy to change. Generally it is better to use a single soldered pack that plugs in for aircraft use. Spring frames are unreliable due to corrosion and the tendency for batteries to fall out.
5. The programming buttons are horrible as is the way the stock firmware uses them. I haven't tried the hack firmware but I don't think they changed the basic menu navigation.
6. The stock i6 firmware lacks some basic features like a Timer. The i6X improves on this some but is still not that wonderful. However the hack firmware does make some significant feature and function improvements.
If you can live with those things then it's a great little TX that will get you going. You might prefer the ia6B RX rather than the X6B as a first RX just because it is an easier package to use for basic planes. It has iBus available for telemetry and FC use. Banggood sell it i6 and the i6X packaged with it as an option.