I was very satisfied with the ADA8000 which I use in conjuction with a Presonus Firestudio interface. Installation was effortless, I simply connected up the two ADAT cables, power and selected the slave clock setting. That was it. The clock sync'd perfectly and I've had no problems in that department, using the ADAT as the sync source. The sound quality is excellent also, very transparent- in my setup I feed in 8 line levels only, so I can't comment on the mic preamps. I use my audio interface for miking.
The only drawback I would comment on is that the unit would not function very well as a standalone mic pre-amp. This is because the mic-preamps are routed directly to the ADAT out. It would be great if they could be routed to the analogue outputs. I would imagine an ADAT cable could connect the outputs to the inputs, but this would introduce an unnecessary analogue-digital-analogue conversion. Small gripe and it doesn't really affect me.
Build quality is great, very solid. Overall, very happy with my purchase.

I know the Behringer stuff is generally the cheaper end of the market, but for what it does, you can't knock this piece of kit. It's plug'n play, simple as that. If you're not too concerned about some (very minimal) hiss in the background when driving the unit at volume, then it's great. I use it for miking-up the drums. It's just the job for that. But, hey, you get 8 extra inputs using ADAT which simplifies matters even more. It's one of the Behringer units I suggest is a must. You know it makes sense at the price.