I've had my Replenish for 2 weeks, upgrading from a Treo 700.
Battery life is worrisome, though OEM spares seem to be cheap and work. If you turn on GPS, battery consumption is huge. I haven't done formal tests, but with the GPS on, I'm guessing battery life is in the 1-2 hour range.
The reception is poorer than my Treo. While sitting on my favorite toilet, my Treo got signal, but was too slow to do anything with it; whereas my Replenish doesn't get any signal in the same spot.
Low internal storage space. I'm already using 90% of my internal memory, and I pushed most of my apps to the SD card.
The screen is kind of dim and hard to read outdoors on a sunny day.
The battery door is not easy to pop off. You need to find a good, flat piece of metal to stick into the pry hole ( I found a nail clipper handle to be perfect).
BT connection with my Jawbone 2 doesn't seem to be flawless. Seems like I have to take an extra step or two to get them to connect after they've already been paired. The same Jawbone was ok with my old phone.
I have not used another droid phone, so I can see that perhaps people are more used to a larger res screen or faster processor. However, since I upgraded from a Treo, I just love everything that the Replenish can do. I do not regret upgrading, but is there room for improvement? Yes.