What are your other MC issues - of you post the link on the MC forum I'll see if I can help.
Just a few things, nothing major -
Limited external player rules (no 'if filename contains X play with X')
No "Play Using" menu to launch a file in an external player if needed, for example if I want JRiver to play everything by default, but sometimes want to view the full disc in TMT, then its easy to just go to "play using" instead of opening TMT manually.
Video cover art is automatically put next to each video file, I prefer everything in one place like a library/ coverart folder, I don't want anything adding anything to my media HDD's.
Mark videos as watched/unwatched from Theater View
JRiver sometimes leaves the ISO file mounted after finishing playback.
I see where you are coming from, and yes I could just manually open TMT5 when needed, but look how much better it is having Youtube/Netflix/Hulu on the JRiver video menu, sure you could just manually open them in Windows but is so much nicer not having to leave JRiver Theater View.
Ideally I want to turn my main HTPC on, boot to JRiver Theater View, and never have leave it to do anything, just sit back and enjoy 8).