Yes
No, Don't own the higher end units.
Yes
No
Yes
No I'm actually a new user to Digilents offerings and haven't had a need yet to use an SDK.
With respect to the last two questions:
Right now I'm happy with the 2230 and its bandwidth, Sampling rates needs vary. As far as current and future needs there likely is a need in the future for more channels and even better isolated channels. Ideally more channels with out a significant loss of sampling rate. Realistically though my interests are more industrial so extremely high bandwidth / sampling rates are seldom needed. In any event more channels, including a trigger channel go a long ways.
As for features or improvements, in all honesty I'm a new owner and have not had a lot of exposure yet. However that has never stopped me from making suggestions: (realize I'm a new owner / learner)
PC's these days almost always come with some sort of "Sound Card", I'd like to see these used via another instrument that is always available and can handle basic oscillator duty. In fact you can literally call it an Oscillator instrument though most sound cards can do better. Now I realize that we have the WaveGen Instrument but I look at this as additional capability and frankly parallel capability that does not interfere with the channel to the Analog discovery.
A higher voltage range on a per div spec. This would make the platform even more useful.
Add supported external DVM's instead of or in cooperation with the Analog Discovery. These days that means a USB interfaced DVM's. The idea would be zero effort implementation on the part of the user, even if that means a limited number of DVM's. You can never have too many DVM's available and sometimes you need the safety of system multi meter.
I will likely have more to add as I learn about the hardware and software. I'm especially interested i how the logic instrument works with slow electromechanics.