Speed improvement depends heavily on the number of commercials.
If there are no commercials, just conversion it wil be a 5% to 10% improvement due to tweaking of profiles
If there a lots of commercials you will see a 30% to 50% improvement depending up on the amount of commercials sicne now commercials are removed BEFORE the conversion.
Regarding the skipping cropping, yes you're correct it's a bug I'll fix it in the next beta build tomorrow