mrlanrat : check out the wiki for full explanation, but searching is not so easy. there is no attribute of a street that identifies it as belonging to a town. it basically guesses by assuming streets in a certain radius belong.
it also doesn't know about towns for searching unless they have a set of is_in tags to provide their relative position in a search heirarchy.
as for cpu spikes...i'm afraid it's a pretty intensive app, it's performance (or lack thereof) is the biggest issue for running on tablets.

soupdragon: no idea about gps brands, I'd imagine you'd need a dedicated bluetooth gps. not sure most devices would let their gps component be used by anything else.