I bought the 922 to be a good DVR now, and a great networked device over the next year. People have reported some bugs (fortunately I haven't been on the receiving end of most of them), and I assume those will get fixed - they just look like young software.
I don't think the Sling portion of the 922 is quite ready for prime time - there are issues with respect to the 922's visibility on the net, and some browser issues - but again, I assume that Dish and Sling have a vested interest in fixing them.
Where I really get excited about the 922 is a bit off topic of your question, but I think that Netflix, Hulu integration and Google TV, along with a (hopefully) matured Sling functionality will make it a killer platform for the next couple of years.
So I'll come back to your question - based on my limited experience, and what I've read, I think getting the 922 is a function of 1) do you think that Dish/Sling will get the Sling functionality solid in your timeframe, and 2) do other features or futures potentially trump that for you?
I'm something of an optimist on both fronts. Part of that may come from recent release from Comcast chains.
Cheers,
Steve