I find that Sony Ericssons are some of the best phones to own. I had chosen this phone to replace my broken down K750i. That phone lasted me a good 20 months and though it occasionally had reliability issues, as with all phones, I decided to stick with SE because they have superior quality phones with innovative features and easy to access menus. This phone did not dissapoint.
The 3G feature has helped me out no-end at university. being a student I have to budget and with some of the nifty features on T-mobile, I am able to subscribe to a complete Sky Sports package with Sky News and CNN included for only £5 a month when it could have cost me anything up to £38 a month with ordinary Sky wired up and possibly more with Virgin Media. The phone does not require an external aerial for this feature and has provided great entertainment even whilst in a queue.
Bluetooth is v2.0 so if I wanted to i could plug in some wireless headphones, which are still fairly pricey buy should go down after next year.
Quite possibly it's only flaws (so far) has been the software CD with it. It doesn't work with Vista (for now) but I'm able to plug it in normally via a USB and drag and drop songs. The memory card that is supplied could also be a bit bigger, 128mb doesn't really cut it these days, so i'd recommend getting a larger card with it (2GB is plenty for filling it up with songs and perhaps a movie too)
Personally, I'd say this phone is better than an iPhone because 1) It has 3G, the 'jesus phone' doesn't 2) You'll know what you're typing and the screen won't get smudged 3) The camera is better, 3.2 megapixels, 2.0MP was so 2005. 4) The upgrade for the K810i looks like it has an odd keypad layout (k850i) so this is the best looking phone in it's class.
Otherwise, a simply brilliant phone. Well Done Sony Ericsson, have a gold star.