Matthew,
I bought two S7700's off of eBay last year (both sellers claimed "not heavily used", and neither had the original box (probably not audiophiles)). Had one modded last summer, keep the other one as a spare.
My modded one had a problem two weeks ago (just before HE2005), so I sent it back to EA. Steve contacted me this weekend to let me know that something must have jolted the unit (probably in transit to HE2005) and caused an internal part -- a rectifier -- to bend in and short against the power supply board. He said it is easily repaired at no charge to me and is sending it back today. He's also making an adjustment to prevent that from happening again.
Asides from this shipping/transportation-caused issue, I've had no problems at all with my EA S7700...and I use it easily an average of 5-6 hours per day over the last year...