sounds to me that in your case, you may not what to fix what isn't broken.
However, as a treo owner, you may find that you can't move as fast on this phone as with the treo, due to the lack of immediately accessible hard keys on the face. I was watching a guy with his treo this weekend, and he was just flying on that thing. I've never had to really power-use this, like taking notes in a meeting or something. Therefore, if you are well-experienced with the treo, you may be kinda stuck with the treo.
I just have this image of you trying to whip this thing out and snap it open, and it just goes flying across the room. :/ But that's what TEP is for
New hardware is always going to be a crapshoot. I felt comfortable buying this phone because I decided that it would have to be at least as reliable as the mogul. Mind you, there is a bit of a learning curve to achieving maximum reliability with the mogul. I've had it totally crash on me once while i was on the road, and I had to hard reset. I had enough info on the storage card to get me by until i got home like 3 days later, but that was it, and I managed to survive.
I drive truck, and the mogul did it all for me, phone, gps, internet and music. I expect this one to do it at least as well, and the extra memory alone tells me i won't regret my decision.
At it's heart, it's a windows mobile device. It has come configured from the manufacturer in the way they think will sell the most units. However, we are not committed to the manufacturer's vision, so we can tweak, enable and disable to our heart's content.
My biggest regret is that this phone still seems to use the same standard touchscreen interface as all phones, and I would really like to try one with the capacitance input. Mainly because this phone requires a plastic/flexible cover, whereas the other ones can be made of glass or something much sturdier like hard polycarbonate or something. I worry about scratches. However, with the flush screen on this one, installing the screen protector is a snap and driving it with your finger is pretty good. might have to press hard on the corners, but that's it.
In the end, i'm guessing you could afford to buy this phone and keep your treo handy for a test drive. Buy it, try it, if you don't like it, sell or return it.
My opinion, this is a very solid and well put-together phone, and it feels so -nice- in my hand.
oh, and as far as the speaker goes, i almost always use a headset with any smartphone. I think that's probably the best way to go.