I have an XDA II, and had the original XDA before that. What I would say
is that they're excellent PDAs because of the integrated GSM module,
allowing for seamless internet connectivity. As phones, however, they're
not exactly world class. Admittedly, the XDA II is a significant
improvement, in terms of signal strength/seeking - one problem I found
with the original XDA was that if it lost a signal it didn't really want
to try and find it again... It's quite uncomfortable to hold up against
your ear I find, because of it's bulbous size.

I wouldn't recommend it as a phone, but as a PDA it's great. A better
phone with PDA features (as opposed to a PDA with phone features such as
the XDA) would be the Sony Ericsson P900, which I also have, and which I
use every day as my primary phone.

Hope this may be of some use.

Whereas most phones are a phone with a bit of PDA tacked on, this is a
PDA with a bit of phone tacked on. Since the full features of PocketPC
are far greater than that of a phone, you may not mind this because most
of the time you'll be using the PDA side of things and just making the
odd call. I guess it depends on you. Personally I have a phone and a
PDA, mainly because I don't want to take my PDA everywhere I would take
my phone (gym etc) and seperate batterys mean I don't drain my phone
when I use my PDA as an MP3 player.