EXS 24 Logic Sampler Users Group

You can't just use the Performance set by itself - you only get 
legato patches.  Therefore, there are no sustains, Stacattos, Trills, 
etc., plus no percussion except for the harp glisses - basically it 
doesn't have the standard orchestra patches, such as Miroslav or 
Advanced Orchestra.   You can use the Performance set to augment 
existing libraries, however.  But if you have nothing else and just 
want to buy the performance set, you would be missing many crucial 
patches.

Jeff