I have a Sony 590...and it's such a pain because it's Sony and it just won't do everything easily...mkv files for example I've pretty much given up on.
However, it does seem to work when you know what to do except for subtitles.
I have found that it plays .m2ts files without any problems other than it doesn't seem to support subtitles in that file container. It could be my encoder though. The player plays mkv files as long as they are not TrueHD sound or VC-1 video which is major pain since many blurays have one or both of those. Anyway, even when the mkv file plays, or for any m2ts file, I haven't been able to get the subtitles to work. They work fine when played on my pc. I have been using DVDFab.
My last thought is the subtitles thing might be the DVDfab software I'm using, maybe a different encoder will make a subtitle playable file, but I haven't had time or been able to work that out yet. Seems almost trivial until you realize they are not present and they appear more than you'd think in movies because of foriegn and alien languages - I like Sci-Fi.
Bottom line, the 590 has played everything I've thrown at it in the highest possible quality, LPCM, TrueHD, DTS-HD MA, off of a USB hard drive, flash drive, burned to disc as long as it has been in a .m2ts file - no matter the codec used, H.264, MPEG 1,2,4, VC-1.
The only problem with m2ts is it seems it doesn't keep chapters, not usually a problem but mkv is nice because you can use the chapter ahead function like with a regular DVD or Bluray.
Oh, if burned as a bluray disc, BD-R, in other words the BDMV folder structure I haven't had any issues whatsoever playing any codec/subtitles.
Almost forgot, one other issue, although I haven't noticed a real difference when actually watching (which is nice), any file played, versus a bluray disc will only output in 60Hz. (I have a 120Hz TV so maybe that's why I haven't noticed it). The discs will play at 1080p/24fps, and even if the file is at 1080p/24fps, it will still output at 1080p/60p. Example, I played a BD-R disc and it outputs at 1080p/24fps, but when I just copy the actual m2ts file from inside the BDMV/STREAM folder, the exact same file bit for bit, it will output at 1080p/60fps.
Hope this helps
PS - If anyone has found a Bluray player that just seems to work, play everything easily, please post! In other words, If you can just "remux" into mkv and save burning a BD-R I'd like to know so I can buy one.