I've heard some stories on the Metric Halo list about some manufacturers' implementation of ADAT being less accurate when it comes to data (losing some packets). But I am CERTAIN that ADAT per se is not a problem as long as you get your clocking right. I have complete confidence in RME's implementation of ADAT, in Metric Halo, and reportedly, also, Yamaha at least at this point. Other than that data issue, the data integrity of ADAT is just fine.
In general, in terms of reliability, professionality, stability, and performance, my personal preference would be:
MADI (preferrred for multitrack)
AES/EBU (second preference)
TDIF
ADAT
Firewire
ADAT is more convenient to wire and run but the non-locking connectors give it lower marks. But the fact that TDIF patching involves both send and return in one cable gives it somewhat lower marks. Firewire is cool, but the latency is potentially higher. The self-clocking in AES/EBU give it higher marks as far as reliable locking even without a WC line. But you need more cables with AES/EBU. With MADI you can get reliable transfer of 32 to 64 channels in a single pair of BNC or SC optical cables. MADI is the most reliable, professional solution.
Hope this helps,
Bob k