Bill, I have used both GPO and JABB for about a year or so and like them alot. They are a reasonable balance between sample size and quality. These libraries need to be modified if you want to use them for live performances. They are designed to be used in the studio where you make use of the the modulation wheel to add expression to your music (volume, brightness, attack and so on).

I found a script to use with Kontakt 2 that defeats the modulation wheel feature so I can use it for live performances. It takes away from the overall quality of the sound but the libraries still sound very good. They are not as good as EWQLSO Platinum, Gold, etc. or VSL but they also cost much less. Furthermore, given that the sample size is much smaller these instruments will also load much faster.

I understand there will be an enhanced version of GPO available soon.

In general, I think a good overall compromise for live performances is to make use of the following:

GPO
JABB
Colossus