I made the same choice that you did - purchasing a high end pre/pro that was two steps removed from the latest models. I have had 30 days to evaluate the piece, both in multichannel and two channel operation.
It was like getting a new system (I used an H/K A/V receiver as pre/pro prior to getting the HTS). From top to bottom, I got a wholesale improvement in sound, in every possible area - image, bass, detail. Seamless integration of my subs with the mains (despite no bass management, but I don't miss it). I just hooked it up, configured inputs, and got good sound right off the bat. Quite good in 2 channel, especially considering that the 2 channel is digital (no analog pass through). It's good enough for me - but I am not as demanding as some.
I, like you, did not want anything beyond 5.1, but I wanted a pre/pro that would be a good unit in my only, do it all system. I could not afford the latest - but I got the sound that I was looking for. I can live with the warts (2 sec delay when starting program material is the big bug, but otherwise works smoothly). I also like the 4 digital outs. I have seen and heard the piece hooked up on the showroom floor as well - so I was familiar with it for some period before I scooped it up on the cheap.
As the previous poster said, don't get hung up on the fact that you don't have the latest model. The piece is by no means perfect (and you'll find that no pre/pro is, no matter how recent - you'll find something that bugs you). What matters is not what you read - that the HTS is out of date, that it's not worth owning - but what you hear. Hearing it in your room, with your gear, is what matters. If you don't like it - sell it, and be done with it. But if you like the sound, don't let the comments on the web tell you otherwise. It was a great pre/pro in it's heyday, and it's still a good 5.1 pre/pro. One man gathers what another man spills.
For the record, I'm keeping mine.