Can't speak for Newblue. When I tested Mercalli late last year I wasn't really impressed. But I seem to be in a minority. Many others praise it a lot.

Personally I am still using Deshaker 3.1 with "extreme" settings and I'm generally happy with it (and of course it's free). I have it set up to be fully automated from the Vegas timeline using a script workflow developed by David Arendt, John Meyer, Willem Theron, wwaag etc.. Highlight the event(s), start the script, choose "add as take" and/or "Add to new track" and the rest is automated. Huge timesaver. One of my scripts can be seen here (will need substantial editing to work with other users' specific setups).