No, nothing negative to report - I did an upgrade install, finished everything in 15 minutes then proceeded to installation of the 10.8.1 update. Only niggle: it asked me to re-download 10.8 again (probably because my Install software was not on the boot SSD). Safari is, indeed, blazing fast and all other apps I had on my iMac continue to open without issues. Repaired permissions before and after, of course, and applied all possible updates before going for ML. Geekbench before (Lion): 11833 Geekbench after (ML): 11839. Mac continues to rule.