You can side load flash and certain browsers will then run flash and there are a number of browsers that handle flash reasonably well on Android.
Relative to going to a tablet for all needs, a lot depends on one's use profile. For work for me, no way. On vacation, I've gone over completely to a tablet. In fact, I ditched my Nexus 7 3g for a Samsung Mega which fuses my phone and tablet into one device. My wife travels with her N7 3g. We take along a full-sized bluetooth keyboard. All together, with smaller power supplies, etc, much less bulk and all the functionality.