I've had Hopes (various models but 2004 was my last set) - really liked them but they did need time spent setting them up to get them right...I used to bleed them every 6 months only because I was convinced I didn't bleed them properly so figured redoing them 'regularly' would stop them becoming a problem - never did have a problem and they stopped very well. No squealing but plenty of power.
Then I went onto Hayes as they came with the bikes - Hayes 9 Carbons - very good for stopping but did need a larger rotor on the front but also felt very on/off - but that is how I like my brakes, I'm not keen on flexy/squishy lever feel. These got replaced with some Hayes Stroker Carbons - slightly more power, nicer lever feel around the finger and the feel wasn't quite so on/off (and I found myself actually liking it).
Tried some Shimano XT's (with the servo-wave) - great power but the 'squishy' lever feel put me off - if I could live with that then they would probably be my brakes of choice - plenty of power, dead easy to set up but a squishy lever feel due to the servo wave bit - this squishyness also means there is a lot of lever pull - which I don't like either (downside is the pads tend to be closer to the rotor so rub more if you want a shorter lever pull).
Now back to Hayes Stroker Carbons (again came with the bike) - these have been excellent (better than my first pair for some reason) BUT the lever developed real stickiness so I got some new pistons - levers got rebuilt but major problems with the brakes when they were rebleed - only 9 months old but the o-rings in the bleed nipple had corroded, then when that got sorted, they wouldn't hold fluid - kept leaking out the bottom of the nipple. After that got fixed, the system got bled (and bled some more just to be sure), and I now have oceans of lever pull and no stopping power - the bleed process is very simple and from what we can tell, there is no more air in the system but the feel has gone to pot. If I can afford to junk them I will as I'm unable to slow my speed (I either need to point up a hill or coast to a stop on the flat - hard to do offroad!).
Whilst my current brakes were in being fixed, I had a temp solution of a Formula K18 on the rear (was junk first ride out but started feeling much better afterwards) and a Shimano SLX on the front (which just didn't seem to work at all in any condition) - the amount of lever pull between the 2 systems was different as well so it was very difficult to find a balnace between them...out the 2 I'd have the Formula's but they wouldn't be my first choice.
My mate has some Formula The One's on his Cube Fritzz - they seem tremendous - a very nice lever feel, seem to have oceans of power and so far have been totally trouble-free - if I had the cash I think I'd be after a set of those.
Saying that, the Shimano Saints appear to get good reviews in the mags, web forums and rider feedback...I'm just not convinced about the amount of lever pull needed as I just didn't get on with it.
No real consensus (even between versions of the same model, I'm having different experiences), so it is very much down to personal preference and experience.
Good luck.
