Had a pair of the 20-2's for about 6 months now. No problems that I can note. Not the most friendly of speakers to power off and on, as I get a bit of line noise as the amps power down. I leave them on all the time so its nothing I would worry about.
I had them first installed in the office system. Small room with a good deal of clutter. While a great sounding speaker, with a good bit of bass, I simply found them wanting a bit in the small office system. Bass is present, and very well done, on par with the old Celestion Sl-600 or SL-700's with an overall better mid range if memory is correct.
I later moved the full range speakers up to the office and put the monitors into the main room with a sub. (revel B-15a) and much larger room roughly 17x22. While the full rangers are more complete if not a tad congested in the little office, the trade off was well worth it in terms of the ATC's. With a bit of room to breath and bottom end help they are truly magical.
I like the powered option as it gives me less to worry about day in day out, fewer moving parts, cables, etc to mess about with and I can just sit and listen. I would agree that you need to go with the best pre and front end you can afford to get the best out of them. The difference between a decent mid range cd and a high-end transport and dac was not minor. Nor was the difference between a low end table and my Rega/Van den Hul setup.
Overall I have had no problems if you like monitors and can live without the very bottom end (as with any monitor) and I think a bit less so via the 20's then they are really a great speaker, and should be on your short list.