Finally, a device that does everything -- and I mean everything. From wifi to 3G you'll never be disconnected (in the UK, at least); I advise getting a contract that allows for a lot of data, with good 3G coverage, because this beauty is really worth it. I find Skype works perfectly, although you really do need a headset (it comes with a wired earpiece).
It's quite large for a phone, it's slightly smaller than my Nintendo DS but bigger than any other gadget I've had, but the keyboard more than makes up for it -- a smaller device would be impossible to type on. It's just about as small as it can be while still being comfortable to use. Also, the screen brightness and clarity is top notch - mine even came with a screen protector - although don't rely on the built in camera to be much use.
If you're a data user like me then you'll love the fact you can never be far away from your email. The keyboard makes typing really easy, far far easier than pecking out letters on a touchscreen, although the swivel screen means you can use it like a traditional portrait PDA too. I've not had a problem with battery life - it charges via USB so if you're never far from a computer you can keep it topped up.
If you have large pockets (or you're female like I am and thus carry a bag!) it's an ideal buy -- it'll replace your phone and PDA and maybe even your laptop too. Beautiful piece of kit.