Disclosure: I recently switched to Android from iOS.
The dropped calls and coverage issue are overblown. It is not like any carrier has a magic cure to the vagaries of radio reception. CDMA phones might have some edge on reception, but those tend to be offset in the area of battery life. In any event, I think coverage is in a 'good enough' phase now.
The real problem is that so many android phones sold in the US are not running 2.3, they're stuffed with un-deletable space-wasting crapware, and they often have absurd carrier restrictions. I think it is very conspicuous how the most happy android customers seem to be the ones with phones that do not have carrier mods.
I could definitely recommend a Nexus S to my mom and expect her to be able to use it just as well as an iPhone _now_. I do not have the same feelings about the other phone I tried (and returned), the AT&T Samsung Infuse.
That's practical advice, but I still haven't unpacked after moving to Canada to get affordable medical care.