What to look for in an induction stovetop?
If you like to cook using 3 or more elements at once, ensure you buy a sufficiently powered model. There's nothing more frustrating than upping the power on one element and watching another one reduce at the same time.
Touch controls look nice but they're horrible from a usability standpoint. I always had problems with responsiveness with wet or greasy fingers. 
Cockroaches love induction.  I don't know if the frequency attracts them or it's just the heat but they will come and eat out the wiring, even if you've never spotted one in the house before. It's a common problem as it's hard to seal the electronics for thermal reasons. Board replacements are expensive. It's one item I would consider an extended warranty on.
As for any 2" cooktop, larger pot/pan sizes can't be accommodated if you're using 3 or more elements. Go 2'8" minimum.