been using my mini with plex 9 for a month or so now.
initially very impressed with the abilities of the program, especially the way it scrapes information for all the imported TV programs, providing title, synopsis, artwork even music. very clever.
plays my HD mkv files a treat, which is the main reason i bought the mac mini
have to admit the way it handles video from TV to iphone without losing it's place is superb.
a few annoying bugs though. i had loads of grief trying to get the mac to sleep properly, and stay asleep. i've mostly resolved that now, but not 100%.
audio has a habit of switching back from HDMI to internal speakers for no apparent reason.
also annoying is plex's inability to play dvd video_TS files smoothly. they play great in VLC, quicktime and frontrow (which i assume is just quicktime again), but are rubbish in plex.
not alone in this, and there's no answer on the, very busy, plex forums.
been wanting to try out MiRow which is a Frontrow extension from firecore, who make aTVFlash for apple TV. unfortunately it's $24 and no demo version available.
firecore just twittered that it's $10 off, today only, so i downloaded it and will try for comparison. i think it is still very early days for the program, and is itself a bit buggy, but we'll see.