I've got a Windows 7 Media Center desktop (tower PC with Intel i7-2600 w/onboard HD2000 graphics) combined with a SiliconDust HDHomeRun Prime 3-tuner cablecard tuner. I use this (or an XBox 360 in another room) for live TV/DVR. I've also got a couple of Apple TV (gen 2 and 3) which I use for Netflix, Hulu+, an occasional iTunes movie rental, and AirPlaying Pandora from my iPhone. For my HD movie collection, I use the WMC server (or an Atom/ION nettop in the other room) using the Plex UI, but could possibly be persuaded to use XBMC (which I already have experience with), if it does a better job with some of the plug-ins/channels I want. We also use the Plex client app on our iPhones/iPads.
My goal is to have a single box and common UI for playing most/all of this content. Unfortunately, I'm thinking that this is a holy grail that doesn't yet exist. Recently, I decided I'd see what the current state of the tech/apps was like with my main WMC i7-2600K PC. Since this computer should be more than capable enough to handle anything, I figured I'd use this for testing. So, on to my experiences...
1) Netflix. WMC already had a Netflix icon on the home screen, so I took a look at that, and it seemed pretty decent. I didn't spend any significant amount of time comparing the user experience or streaming picture quality between my ATV and my WMC HTPC with the Netflix app, but my initial impressions were positive. I have not yet tried out Netflix under Plex or XBMC, and am not even aware if working plug-ins/channels for Netflix exist for those. I'll need to do more extensive testing to see how the UI and PQ compare to what I'm getting from my Apple TV (which I've been very happy with).
2) Hulu+. So far, this looks to be a miserable experience. The Hulu website makes no mention (that I can see) of even having a downloadable app for Windows. You have to add /labs to the end of the URL to find it. Anyways, I got the app and installed it, but: a) It doesn't integrate well into WMC and a hack I found online to add an icon to the WMC interface still didn't work well for keeping the focus on the proper app (probably something I can fix, though); and b) The Hulu app's UI would start ignoring my remote control presses after a while. My first attempt to play something also resulted in them serving up what seemed to be a non-stop barrage of ads, followed by it playing the Jimmy Fallon show (which wasn't the show I had selected!). After shutting it down and restarting, I tried to play the show I wanted again, and this time it played a single ad or two and then my show, but it again stopped responding to my remote. Overall, the whole experience felt buggy, but I'm willing to give it another try if anyone can offer some suggestions. Again, I'd also like to know what options exist for Plex and XBMC. Right now, I'm happy with the UI and PQ with Hulu+ on my ATV.
3) Amazon Instant Video. I'm an Amazon Prime member, so this would be nice to have. I haven't tried the standalone Windows app yet (it looks like you have to download the full show or something, which seems to be oriented more towards taking a show with you on-the-go, and there isn't a Mac version). There's the option to stream from the web, but that would require a keyboard/mouse. I don't know if an XBMC plug-in exists. My previous attempts at trying the Plex channel were unsuccessful, but a new update seems to have fixed it on my iPhone now. My Mac is still getting errors with it and I haven't tried it again on Windows yet.
4) Other VOD services. I may want to occasionally purchase a movie or TV show rental. What are the best options out there? Again, my ideal is a channel that runs within Plex and offers a UI consistent with Plex. If not Plex, then what about WMC or XBMC? Services might include iTunes, Amazon, or VUDU. Remember, the UI needs to work well with a remote.
I'm interested in hearing advice as to how to get all of these things working, ideally under Plex. If not Plex, then WMC or XBMC. I'm also interested in hearing about your experiences in using these on an HTPC and how they compare to the ATV and/or Roku experience (I don't have the latter, but am curious). As of right now, it seems like in order to get the best experience, I may need to accept the fact that I'll need at least two devices: an HTPC (for live TV, DVR, and movies), and an AppleTV (for Netflix, Hulu+, and iTunes).
Also, if you're aware of any major issues getting an acceptable playback experience with the Intel HD2000 (or the HD4000 that a Mac Mini I also have uses), let me know. I believe on my WMC server w/HD2000, I had to turn off GPU decoding in Plex and XBMC because of video defects I was seeing, so that box is using the CPU for movie playback. I'm not sure if WMC utilizes it or not. In a brief test with my Mac Mini (under OSX), I didn't seem to have any problems turning on the GPU decoding.
I'd much rather watch a great movie in B&W at 240 lines of resolution than a lousy movie in 1080p with lossless audio.