I've used them, but only for testing. Wouldn't bother with one as a phone for reasons already stated. The whole thing feels bloated, with poor response from the GUI (the most important phone feature IMO). Battery life is 1 day of standby time on 3G but improves a bit on 2G only if you don't use all those bells and whistles.
Yes, it's got a good camera (why would I want one when I've got a digtal SLR?) it's got an MP3 player (so have many better phones) It's got GPS but then I've got a hand held GPS, and a TOM TOM. Rolling all these features into your phone detracts from what you spend 99% of your time trying to do with it IMHO - trying to make phone calls.
The GPS supports assisted GPS which in theory gives a very quick position fix but be aware that the firmware that's currently shipping (from Orange at any rate) doesn't support this, as I found out to my frustration

So you're back to a standard GPS that downloads its' data from the GPS constellation at 50 BAUD. Expect to stand around for a few minutes while it gets its' act together. Phone comes with a few lame positioning applications but haven't seen a convincing reason to have it yet.
I've just reluctanly chopped in my ageing 6310i for a 6300. It has MP3 player, a camera, radio, etc. (none of which I really want) but is much nicer to use than the N95 and it's nice and small (bit to small, IMO. looks like it belongs in a handbag

and requires dainty little fingers to use). Battery life is not great compared to the 6310i but it will do a couple of days between fixes in real life. With an N95 you'd have to be close to a charger 24/7 IMO.
Despite the fact that I see a lot of phones in the course of my work I don't see many that I'd like to have for myself, at least not after the initial novelty has worn off - hence sticking with the 6310i for so long. My opinion is that you can always use a phone to give a PocketPC connectivity and that way you can leave the PocketPC at home and have a nice small phone when a phone is all you need.
Kevin