I just want to report my experience after a grueling couple of days.
For various reasons I need Live to sync to my external hardware. It has always been a bit wonky, but it worked. Since somewhere around 8.2 and onwards -- with the reported "better" external midi sync, on my Macbook Pro (2.6Mhz, 6 gigs of memory, HDD) running Lion, as soon as I hit record (recording 20 tracks at 44/16), using a Motu 828 and Pre8 via firewire, I get massive crunchy dropouts about every 15 seconds even though the computer use shown in live is around 18 percent or so throughout. These drop-outs can be increased like crazy if I move away from Live while Recording and do anything, like open finder and search files (on different hd than recording to even) or open a webpage on the browser (not that I usually do this, but here for testing purposes).
Using the same setup, but using Internal Sync, like before the 8.2.6/Lion combination, I can record the same amount of tracks and do almost anything in the background -- load webpages, search the hd, etc and ZERO dropouts unless I really push it.
I tried everything to lose the dropouts with external sync: Changed midi interfaces, changed clock source, etc. Nothing worked. Very upsetting as I have a performance coming up.
Solution: Since I dual boot to Windows 7 using a Bootcamp partition, I installed 8.2.6 on the same Macbook Pro in Windows 7, loaded the same Live set and configured the motu interface until everything was the same as in the OS X boot. Viola, rock solid, full recording of all tracks, no hiccups or dropouts whatsoever, can multitask like crazy (although I wouldn't in a live show) and still no dropouts. I could be just happy to hear clean audio, but I even think the sound quality is better than the OS X version.
I am truly relieved but somewhat irritated I had to go through all of that.
It it goes to show that there is something seriously wrong with the 8.2.6/Lion combo compared with the 8.2.6/Win 7 Combo when it comes to stability using external midi sync.
I'll be running Windows 7 on my Macbook for music for the foreseeable future for a very good reason at this point.