In the world of sample libraries, there's always something new. Always. It's become a crowded industry--and that's a good thing! Competition is good, and it's bringing down prices (well, at least sale prices), more freebies offered to entice other people into this noble profession, and in general pushing the boundaries of what people might have thought possible a few years ago.
But to be honest, a lot of it is superfluous. Awesome, exciting, fun to play, intriguing, beautiful . . . but superfluous. If we're talking about orchestral scoring, you may want that new library that is going to give you that 5% (or maybe even 1%) difference that makes your sound a bit more unique or realistic, but that's fairly pointless if you don't have the basics.
BBCSO Professional is my base, my foundation, my starting point. As a good friend calls libraries like this, it's my "bread and butter" library. I use it in almost everything. And quite frankly, given the cost, I should be using it that often. This is $999 not on sale, coming down to about $700 when on sale.
It's not the only choice, of course. Some people don't like the Spitfire interface. Some people complain of programming oddities that occur (and yes, they do occur at times). Some people don't like that it's wet out of the box. That's all valid. But it doesn't matter to me, because I can magic with it. The French horns are so good that it makes me want to put more brass in everything. The sound of the room is stately; it's not so wet that you can't pair it with another reverb or room sound and make it fit, but it's not so dry that until I put on a reverb it sounds farcical. It has appropriate orchestral sections and solo leaders. The legato patches, when played well, are delicate and nuanced.
It's not the fastest or best for making quick sketches. It's not (always) bombastic enough to create a Zimmer-like feel. But it's beautiful. I quickly wrote this the same day I got it installed:
And that's why I keep going back to it, and it will always be a staple in my compositions. It can get me most of the way there.
Of course, I don't just want to go part of the way, which is why I have a few (*cough*) other libraries in my arsenal.