Hmm. I have 60i footege, and want to use as 50i (with little slow mo of course),
but without interpolating. So this method dont work for interlaced video?

I edit exclusively in Vegas, but any retiming or frame rate changes i need to make i use TMPGEnc 4.0 XPress. I find it does by far the best correct conversion, even for NTSC to PAL, much better than the poor job Vegas does. It also handles cineform files if you are working with them.

Built into TMPGEnc 4.0 XPress is also a good video noise filter and some other worthwhile filters not in Vegas, so they are a bonus.