i had the majority of my BPU+ (rltc, suspension, cams, fmic, bodywork etc etc) work done at the old Torque IC and Zac (the head mechanic there then) seemed competent enough as i have not had major problems mechanically (the current situation with the blown turbos i believe to be a separate issue altogether due to time having passed since), so maybe a lot depends on the variables simon mentioned - the amount of money you spend, luck, your own mech knowledge and how well you get along with them and not the least also - your knowledge of the market!
i have heard other people mention horror stories about them but then again it 'seems' you get that from most other shops (mostly coming from simon i must add! just kidding). having said that, there are also a lot of people who have used these self same tuners/garages etc and have been happy with the work done. the idea that some maybe better for certain things than others is a purely personal issue i feel. as matt said - you can please some of the people some of the time but not all of the people all of the time.
the best way for noobs to figure where to go for trusted advice and good work would be to ask some of the older hands what their experiences have been as well as what they have reliably heard. i started off on the wrong foot with my mods (my own fault) but after having listened to the likes of john, leon, matt and terry (whom i trust), i figured out the right and wrong ways and times to do certain things. people will always be willing to help - especially on this board, you just have to ask.
all this aside - i have never heard a truly bad word said from people in the KNOW about the likes of Matt, John, CW and Leon. my 2p.