Hollywood Strings is a great library, and where the most realistic sounding articulations and passages are needed, it is the library I turn to. For broader brushstrokes and more general string arrangements, I tend to use my other libraries, like Albion One, Da Capo, Grosso, or even the Kontakt VSL strings (which are dated but quite useable under the right cirumstances).
Same with brass -- Hollywood Brass' legato patches are really great, especially for solo trumpet and horn passages. For passages that need brass instruments in broad groups, I tend to use Albion One, Da Capo and sometimes even Garritan Personal Orchestra 5.
The most serious issue I have with EastWest is with Play, which is the most unstable of the VST sample players that I use. I have no concerns with other engines at all -- Kontakt is like a rock, and I can run a million instances of it without any issue; Engine 2 is fine; and the Aria player with Garritan is perfectly stable. EastWest Play generally works, and I can load multiple instances of it without too many issues...usually. But in the rare moments when Sonar craps out on me, it almost invariably happens when I'm loading a patch into Play.