According to RokuTom on this official post, all Roku 2 devices support Dolby Digital Plus 5.1 pass-through and subtitles. I had a chat with a Roku tech to verify this, but didn't get a definitive answer.
I personally don't see much value in utilizing my Roku as a gaming platform, but who knows? In a few years when my kids are older, they may see things differently.
So that leaves me thinking that the only significant differences between XD and XS are:
- ethernet on XS
- motion sensitive remote for gaming on XS
- instant replay button on XS
But I know that all Roku's also have builtin IR ports for working with universal remotes -- I have my Harmony One controlling my Roku 2 XS just fine. But do the XDs have the instant replay feature enabled in IR? Could you send the instant replay IR command to an XD and would it skip back?
If so, I think I would have been just fine with an XD instead of the XS. My results with the wireless on my XS have been stellar so far. I've rented 2 TV shows from Amazon, watched a few other shows on Netflix, and some other miscellaneous channels without ever a studder. So it leads me to think that having the crutch of an ethernet port is really a bloated feature.