Looks like it is 1-2% faster in the javascript area (ive been timing it). They are 2-5% on the year so far since v4.
I think the faster release schedule is kind of cool. I do not have a problem with it at all. We get the stuff pretty close to when it was done. Instead of waiting a year and a half for everything to be done. Plus most of the stuff has a decent cook time before being moved into production. MAME is basically at version 143 yet nobody really bitches about that...
The down side is it looks like they are doing less now. Even though they are doing about the same amount of work...