pretty happy with the Popcorn Hour (PCH). in that week, i've used it primarily for video playback. its UI is decent, but its quicker to browse through media using the 360. what's great is the Popcorn Hour is very quiet, except when a harddrive (optional) periodically spins up, and that is loud. need to switch to using a 2.5 inch harddrive. random access for video (and music!) playback is very customizable. you can fast forward/reverse (some formats dont reverse yet), goto a specific time, and press 0-9 to jump 0 to 90%, as well as 30 second jumps forwards and backwards. it does not (currently) support resume from where playback was stopped, which i dont consider an issue since you have some many ways to skip around. it also supports multiple subtitle formats (with options), and multiple audio tracks. what's odd is the PCH doesnt have an off button. it occasionally got into a bad state where it would stop playing videos, but it wasnt fully locked. to get around this, there is a remote control button sequence you can press. just added that as an additional button to the harmony remote, and its no longer an issue. for normal operation, chances are that i'll hardly ever need to reset it.
for content, it can access UPnP Servers and file shares. one nice thing is it looks like it can access password protected media shares, like what the Promise SmartStor exposes. it does not currently see the UPnP AV service from Infrant ReadyNas. the ReadyNas has another service called 'Home Media Streaming', if i turn that on, the PCH can see it ... but the UI sucks. it can also see the ReadyNas as an SMB share, but i enabled NFS for faster speed. you can also install other services on the ReadyNas, but i'll hold out for the UPnP AV issues to be worked out. the PCH can see the 'Windows Media Connect' service from Windows Home Server. but i have some issues when i'm browsing around (white screens of nothingness). WHS doesnt support NFS by default, so i'm just using it as an SMB share, which is fast enough for SD and 720p content. for 1080p streaming, i did install the myihome UPnP server on my media center PC. myihome also comes in handy for shuffling music video directories. finally, i installed an old harddrive (IDE), so that i could try its web services, but never pushed any media to the harddrive.
for video formats, it has decent support. WMV mostly plays, but i've got a handful that it cant play but the 360 can. MPG mostly plays, but again, i've got some that do not play. granted, the 360 doesnt play MPG over UPnP at all (lame). AVI mostly plays too, including Div3 (not supported by 360). HD MKV plays great, including 1080p content served over UPnP. initially, i could only get 720p MKV content to play because i was using an SMB share, but 1080p works great over UPnP. HD MKV is a huge feature, because that is the format i'll rip my (dead) HD-DVDs to. anime MKV mostly did not play because they used the OGG Vorbis audio which is not supported by PCH (yet). for ripped DVDs, it has menu support and works ok, but i had some DVD files that it would stuttter on (this is bugged for the PCH team to fix). i could play the same DVD rip on the Klegg MediaShare without any issues at all. it also has some MOV support, but i havent had any luck with the few HD MOVs i tried.
that brings up audio formats (for supporting video), which did not fare so well. not sure i understand the issue, but it looks like they did not license DTS. instead, they just pass it out digitally, for your TV or home theater to decode. that mostly works for my setup, but i've had some DTS audio files that screw up my receiver. it does support MP3, and plays AVI files that the 360 might stutter on or fail to play because of an older mp3 codec. but the main issue i run into with MKV is the lack of OGM Vorbis support. if they can get DTS working better, and ultimately add OGG support, then it would improve its video support. i.e. if a video wont play, it has typically been the audio codec keeping it from playing.
for music videos, it can playback a directory of files on an SMB share with the ability to skip next/prev songs. but it breaks down by not being able to skip to a random file. but you can get around this by using the myihome UPnP Server. it introduces a PC back into the scene, but it also allows you to shuffle the files in the directory listing. then you've got a decent music video player. this is a huge feature for me. cough ... stage6 ... spider ... bot. when they update music playback to support shuffle, i'm assuming i can stop using myihome for music vids.
as far as music playback, it gets poor reviews, and the UI team has announced they are reworking it. but i actually like it as it is, because the same tecniques for random access that work for video also work for audio. so its perfect for listening to 60 minutes mixes (and audio books), because i can fast forward and skip around by 10 percent increments. random access for long running audio files is a huge feature for me.
haven't used it for photo viewing. supposedly the UI is lacking
haven't used it much, but it also has web services support for YouTube, Google, Live365, Shoutcast,\ etc.. ends up the YouTube support is not FLV, but it uses the MP4 formatted vids instead. developers can write their own services to display on the PCH as well. i've tried a couple of the services, but the response time is too slow for my taste. i'll have to give these services another chance.
the hope was that the PCH would become my primary player, but it hasnt. the 360 is still my primary player because it has great support for the most common video formats : AVI, WMV, and those formats in HD. if the PCH could speed up their UI and fix the UPnP issues i have with ReadyNas/WHS, then it would become my primary player. the PCH is a solid secondary player for (the many) features the 360 lacks : HD MKV, MPG (over UPnP), Div3, mix tracks, and music vids. the Klegg MediaShare is still a secondary player for DVD rips, until PCH fixes the stutter problem. i still need a way to play anime MKV (from the forums, it looks like PCH will add Vorbis support). to a lesser degree, i'd like OGG video and FLV video support too. but the best part of the PCH is there will probably be a firmware update next month, and some of my issues above will be fixed, along with new features. they are really good at listening to the community and releasing updates consistently. the 360, MCE Extenders, and PS3 are going to have to start extending their media functionality.