My first race day (track day as well) with the B5M Factory Lite was a good experience. I built the car per the manual, (with the one change of running the "middle" setting on the rear hub carriers) and a set of Electrons that had seen 2-3 race days on my B4.2.
I had not been to a clay track to race for about a year, so I ran the old 4.2 for two batteries to get the feel of the track (IERC, new layout, quite fun). I was running about 26-27 second laps. Brought out the B5M-Factory Lite and on the first battery I was .5 seconds a lap faster (on average). By the end of the night on laps that I ran 'clean' I was in the low 24's (the hot shot class guys were in the 22's, maybe 21's).
Now it is time for some practice laps and some tuning adjustments, but the new car was better than one second a lap faster than the old one, not to bad (the last time I remember a car being so much faster on day one was when I bought my B2 in the lateish 90's to replace my rc10 team car (or maybe my XrayT2 vs. the TC3)