im a big fan of bluetooth and have used it for a number of things..
however i also own a Sony Ericsson T610 and an iPaq 3970, both Bluetooth-equipped.
you can sync the PPC over bluetooth and surf the net too, which is way cool
then theres some really good thirdparty apps for the SE, the main one im thinking of is Floats Mobile Agent, which is the neatest piece of software I have.
it will sync up with my Sony Ericsson, load all my phonebook entries, messages, profiles, etc, let me send messages using the PC & phone together, notify me with popups of incoming/outgoing calls, allow transfering of files very easily, and supports scripts, the coolest one which will allow you to use the phone to control your computer.
Theres full controls for Windows Media 9, PowerDVD, Powerpoint (use it as a clicker!), you can control volume, you can move the mouse around, you can lock the PC, control iTunes, and a number of different applications.
Definitely way cool.
I also have a bluetooth headset which I use in conjunction with my phone, its very nice to have...
if youre interested in the technology since your computer is equipped with it (unfortunatly im cursed with a USB adapter) you should try to get a phone that has good Bluetooth implementation (new generation Sony Ericssons are definitely the best there)...
although im afraid that the next iteration of Bluetooth might not do so hot if Intel starts pushing Wireless USB or if phone manufacturers start adopting 802.11x technologies. Whats nice about bluetooth is that its low-power... Ive heard many people wanting WiFi in their phones, but I really dont see the point if the phone is wired (heh or UNwired) for data in the first place, and battery life would be HORRENDOUS until we see some new battery tech for phones.