Just my 2 cents on this old topic:
.mkv is AMAZING for a format when ripping bluray. It also has the ability for a 0 compression rip for those with lesser powered media pc's, aka, codecs do almost no work when playing the video. As for gotsent, I run windows xp pro x64, and gotsent has given me nothing but trouble. I tried three different bluray quality .mkv files, and all of the results came out corrupt to where I just couldnt even open the file on the 360. Also you have to split it into like 4 files! thanks 360!
I am trying encode 360 now, will see if it has some better results, but I have a feeling it wont. It's time to go back online and get a real transcoder to do this(or similar to gotsent, with more quality to it)
Many people have no problems with gotsent, I ENVY YOU! and no HD movie takes 20 minutes to convert, it took almost an hour on that 9GB movie, note the person above said 15min/1GB
Good luck all