Pete,
I was looking for at buying a GTV 3.0 for a few months then test drove a 147 GTA because the dealer had one. Same as you I knew I had to have it as soon as I started the engine!
Had it for 6 months now and no problems at all apart from trawling through this website too often and wanting to mod it even though its plenty quick enough (I'll come to you when you buy one!!!

).
Mines a 03 plate which has the 305mm disks which there's alot of debate about here. The conclusion I've come to after looking at lots of opinion is to change the pads for new standard AR ones (alot recommend Ferrodo DS2500 ones but unless your doing track days its probably not worth it - plus they're £150 instead of £50), change to braided brake cables and new fluid. Ths should sort out the softness which you'd probably find after time. I'm having this all done toward end April (plus a remap and CDA fitted...your time will come I bet!!!). As for them warping - I've had no problems, mind you I've only done around 5k miles over 6 months and I'm no Nigel Mansell.
They use alot of fuel - especially around town where you'll get anything from 10 - 17MPG. On a motorway run I get about 24mpg so not bad. Can use alot of oil, seems to vary by car as mine doesn't at all.
Interior is great to sit in and look at - no rattles in mine. You may want to change the exhaust since the standard back box is pretty ugly - look at Supersprint, Autodelta, Ragazzon.. agin a few searches on here will tell you all you need.
I bought from a good Alfa independant which tends to be most people's advice - same for servicing. If you kow your stuff there's always a few on Pistonheads for sale privately as long as you want red!
Could go on but need to do some work!!
In summary a fantastic car & you can't really go too wrong as long as pay as much as you can afford which I suppose is the same with any car.
Go buy one!!!