bigcat
How do the various string libraries compare to what comes with diamond?
Concert Strings 2 is basically "the same, but better." Same setup, just different samples, more advanced programming, and fully chromatic. I likes it a whole lot and it is what I use most of the time. Pop/Rock Strings is a cut down version of CS2. I don't know the precise details as I don't have it (no need if you own CS2) but it is derived from that sample set.
Spotlight Solo Strings is interesting. Basically 4 instruments, with 4 different soloists each recorded. I've played with it a little and it isn't as much to my liking. Neat idea though. Certainly powerful programming and probably can do cool stuff if you fiddle with it more.
Solo Strings 1 and 2 are just the solo patches from Concert Strings 1 (part of Diamond) and 2 respectively. Just a cheaper pack if you only want solo instruments.
Something to note with the Diamond/CS2 strings is they have 4 sets of strings for each instrument: full, half, quarter, and solo. That is how many people are playing. So full is a full section, half is half the players and so on. You can switch back and forth in real time as needed (and it'll autoswitch for divisi, if you tell it to). It is a nifty feature.