I would concur with everything Kent said above. I haven't used it extensively yet but it seems to work well, is recognized by Pinnacle Studio and Sony Vegas as well as Prism Converter as a codec, and is indeed fast and compact with no noticeable degradation in quality.

I hope this author keeps this codec updated! Great job!

I also use it as an intermediate codec when I'm going to perform multiple edits and renders on a video clip. Another great use is for converting the new (and very problematic) AVCHD MPEG4 video clips to an AVI file wrapper with PCM audio codec so VirtualDub can import them. You can then output VirtualDub in whatever format you like or stay with the Lagarith codec if you are going to further process the output file in another non-linear editing program.

This is my personal favourite Codec. Kudos to the author!! I'd highly recommend it.

It works perfectly for me when used to capture video from my tv card. I find that it's just as fast as HuffYUV and significantly better on compression, which saves me disk space, which in turn allows me to capture more.

I also use it to create an intermediate file whenever I have to perform complex (and tediously slow) editing operations so that I only need to do the slow operation on the video once. I can then use the intermediate file to do a much faster final 2-pass encode, which overall saves me time.