Also, just FYI, when converting your DVDs over to the MKV/.MP4 format you should know that this is primarily a CPU power hog. The faster your CPU, the faster the conversion. So while converting, just click "GO" and walk away and let it do its thing.
I've see Intel i7 CPUs take about 15 minutes per DVD. I've also seen Core 2 Duo's take about 45 minutes or more. So it all depends on your setup.
Don't have a Mac, so can't say how long. But the CPU should be the deciding factor.