The files you end up with after using MTR are not recognized in iDVD, at least from my experience. iDVD expects to render DV files into MPEG2 for a DVD, and the file you got from MTR is an extracted file from a pre-existing MPEG DVD. Not the same. I use Roxio's Popcorn or Toast to burn the MTR files to DVD. The great thing about these programs is that they will "burn to fit a single side DVD", just in case your material is more than will fit on a standard DVD. Sorry, Popcorn and Toast are not free, but for me, they were some of the best money I've spent on my Mac. I've never seen a "free" DVD burning program for the Mac, but maybe I've not searched enough. My Mac doesn't use Front Row, so I can't answer your question about that, but I would assume that it would recognize the file if you save it as a Disk Image (a virtual, playable video file). iDVD will save a project as a Disk Image, but I think it needs a different source file. But Popcorn or Toast will save your MTR video_ts file as a Disk Image. You can play this Image like a DVD without having the DVD in your drive, then burn it to DVD at a later date.
I just used mac the ripper to back up one of my DVDs, and so I have a video_ts file on my hard drive. What is the easiest way to get this file onto a dvd? Will iDVD do this? Are there any free programs out there that can?
Also, is there any way I can get frontrow to recognize this file? I can watch the file using DVD Player, but when I start frontrow and go into the movies tab thing, and select the file, it says "there are no movies available in "video_ts""
Hope you can help me with this!
Thanks!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic