For what it's worth...
When I first set up Logic and VEP I was getting quite a few pops glitches and hung notes until CRUCIALLY I disabled "Internet Sharing" in the OSX system preferences. I was using it to pass the internet connection from my master machine to the slave. But it seemed to f***k everything up. Now all our slaves are running totally offline with only one LAN connection for VEP running on its very own LAN cable with nothing else going down that cable.
We're running 2 slaves systems on Mac Pros with logic, running 240 tracks of (currently) Kontakt 4.1.1, Omnisphere, Massive, FXPansion Sysnthsquad. And they're really running pretty much flawlessly.
In our Logic template I've used the environment to add a special MIDI track for the very infrequent occasions when I get a hung note... This track has all note data removed (using transformers in the environment), and then passes everything else to EVERY midi channel on EVERY VEP instance (routed in the environment)!! This way, if there's ever a hung note, I just unmute the "all notes off" CC message which I keep in Bar -2 on this special "all VEP slaves" MIDI track, and BAM, it's gone. I also use this special "All VEP" track to send Modulation and Pitch Bend resets at the very start of every cue. This way if there's missing dynamics programming on a track, at least the playback results are always consistent.
(Very, very occasionally, I do have an issue with some Kontakt patches hanging _within_ Kontakt. This isn't cured by sending an "all notes off" message. I'm pretty sure this is in fact a bug in Kontakt, or possibly a bug in the scripting of specific patches. Although having said that, I don't think I've ever seen this behaviour when running Kontakt straight in Logic, so it may be related in some way to hosting Kontakt inside VEP. None the less, I've only experienced this maybe 2 times in 3 months, so it's no biggie.)
More useful info for Logic users... I find the following latency settings work best for us:
Audio Buffer: 128 or 256 samples (can be increased during mixing if necessary)
Process Buffer Range: Medium
VEP AU host Latency: 2 buffers
and one last thing. ALL professional Logic users MUST read this thread on the Apples forums about how the currently selected track in the arrange window is in "Live Input Mode" and the entired signal chain for that track runs on CPU core 8...
http://support.apple.com/kb/HT3161
Peace out... and community forums FTW!
Will Rice
p.p. Sheridan Tongue