Not been for a couple of years but we queued for 2hours for Rita and wished we hadn't bothered - it aint even that good!! The ride itself only lasts about 20seconds.
One tip i've found, leave all the 'big' rides until late in the day - a lot of people travel a fair distance to get to Alton Towers, so after 3.30pm the crowds start to reduce as people start to make their way home. We couldn't be bothered joining the massive queue for Oblivion at 11am, but we went back at 4pm and walked straight on - no queue at all - there were spare seats on the ride as we went round!! Do check what time each ride closes though, as they don't all close at the same time.
Check before you go if any rides are out of action. Whilst they arent a main attraction, last time we went, the cable cars weren't working which means we wasted a lot of time walking from one end of the park to the other - would have spent much less time if we'd been able to use the cable cars.
Finally, something i've never tried but have been told by several others - visit on a Bank Holiday Monday. It seems like a bad idea as you'd expect it to be really busy, but it seems most people think the same, and so its actually really quiet. One of my friends goes every year and always goes on Bank Hols and says they hardly have to queue for anything.
I agree though that the FastTrack shouldn't be allowed - just another way of fleecing us and as you say, if everyone that went bought a FastTrack ticket, it'd be pointless. The more people buy them, the less effective they are. And I don't see why they need to charge £6 to park your car too, robbing *******.