I have a TREO 650 from Cingular. All I can say - is that if you're a heavy user, it'll get annoying quick. I've gotten used to it however and it's a godsend esp. if you're traveling - get email anywhere..
The phone section is clumsy and unreliable at best. Small buttons, finicky controls, tendency to simply go "beep" and shut off when attempting a call. Battery life is decent even at 4,000 minutes + a month.
From a PDA standpoint, works well - Palm OS has a gang of cheap software, and the calendars and database management is decent. Interfacing it with a Windows machine with Outlook is good - reliable.
Software can be found and downloaded anywhere. There are more accessories for this phone than all the others out on the market - probably has the heaviest support of all the PDA phones.
http://blog.treonauts.com/
Attachments -Will reciever standard picture extensions, and PDF -Technically the phone can view .PDF files, but that requires a special conversion process so if you do that (I do) be prepared. You have to get it converted on your desktop computer, then upload it into the phone. If you need native .PDF (like if in email) then you're screwed. No way to do it.
Email - Mine came with Versamail and it does a reasonable job of interfacing with 4 POP3 accounts I use, and you can actually do some pretty good work with it. Forward attachments, include attachments, and it's reliable.
All you need to really set up a Treo are two programs - "Volumecare" - out of the box the Treo has terrible handset volume - fixes that and "stopdim" - prevents the screen from shutting off during calls so you can still use the buttons. "Butler" is cool if security is an issue - you can text msg. your own phone and it'll erase itself and lock up so it's unusable.
Internet access is OK, but you're not going to be reaching for the phone to surf if a computer is available. You can enable cookies so you can post to Pelican OT
Since you're on TMobile you'll probably need an unlocked Treo since they don't offer Treo on TMobile - I'm assuming it works since both are GSM. If you're gonna switch service, they just released the TREO 700 but it's Windows OS instead of Palm - faster internet connection but who knows if it works right?
No WiFi in these things yet, but to most no big deal. Bluetooth is built in and works well.
rjp