I took advantage of the free upgrade PE were kind enough to offer SL66 owners at Campaign.
First thing I noticed was that I had a huge increase in FPS. I was chronoing at about 290 as I didn't want to risk a hot shot with my standard SL66 bolt, after changing the bolt I did not expect any change in the dept. but thought to be safe I should check. First shot was 330 then 325 +/- 5 I had been having more trouble than normal with the paint(bad batch, very noticeable seem and dimples, it was chronic by the way) and had been breaking a fair bit with the old bolt this was reduced a bit with the new bolt. After we changed the batch. This also increased the consistency to +/- 2. And zero breaks. I tried it out with a number of different brands of paint and could not break with any.
Weight difference between bolts I don't believe was much.
Overall very happy with the upgrade but I think the biggest differences will show in the winter when more problems occur with brittle paint.