IMO the OTS libraries don't lend themselves to live playing as well as some others. You really have to learn the keyswitches, which aren't natural to hit while you've got one hand on the pitch bend and mod wheel. Needless to say, Greg spent a lot of hours practicing while creating the library, long before making that video. It doesn't hurt that Greg's also a fine keyboard player.
When I record guitar solos for sampled guitar, I use one of the canned patches in my synthesizer to monitor while playing so there's no latency. Convincing fake guitar parts are all about the performance, and an important part of that is pitch bend, which is difficult to program after the fact. After I record the MIDI, I then go into the PRV and add keyswitches to make use of the features that my synthesizer doesn't have, such as mutes and hammer-ons (hammers-on?). My OTS EEG parts always require a lot of editing after the initial performance, but I'm almost always happy with the results.
If you want a guitar library that's super-easy to play live - but doesn't have the breadth of expression of EEG - check out Indiginus' Torch and Delta Blues Slide Guitar. These have velocity-switched articulations and just come out sounding nice no matter what you do. And they're cheap: $50 and $40 respectively. I'll be reviewing DBSG in the next issue of SoundBytes, coming out in a couple weeks.