I put my ATV2 on EBay the day of the announcement. Has Season Pass installed and it sold for $131. Shipped it off today and the ATV3 arrives by FedEx tomorrow.
And none of them work with the Apple ecosystem (read: iTunes) and offer the simplicity of ATV. So it's a trade-off, like most things in life.
AC3 is fine for most folks. Hell the people I know don't even use AC3 most of the time just play back the AAC stream on crappy TV speakers. Not all folks have expensive high-end audio systems, remember that.