Well, the Synchron Strings had a difficult birth, and there was a lot of ill will around at the time, so there is a lot of historical negativity around this thread - but I think a fair bit of that is now out of date.
I am actually loath to recommend to buy or not buy any library, as, particularly with string libraries, they are so personal. It's like picking a new shirt out for someone. So with that Caveat Emptor in mind....
For me, with Synchron Strings, here's my thoughts - The shorts are particularly good - I like them very much and feel they are the strong point of the library. The longs are fine, without setting the world on fire, and the Cantabile is very nice indeed, but not so much for faster tempo lines. The mic positions (I have standard) are good enough for what I need, I don't really feel the need for the extra mics in the full library. I have managed to use the mics to get anything I've really wanted out of them, but then, I'm normally fitting them in with other Synchron libraries. If I didn't have it, I would buy it again, but would be happy to wait for it to be on sale or such like.
Which brings me onto other things - since buying Synchron Strings I, I have also picked up during various special offers and 4 for 3 vouchers, Chamber, Dimension and this month I finally bought Appassionata Strings.
I am loving Appassionata strings - it's perfect for that lush John Barry sound (Out of Africa, Born Free, Dances with Wolves and Bond). But if you don't want that sound, well, it's a bit big.
Dimension is more about the writing to me. As I am learning more and more about orchestration, Dimension Strings enables me to write for standard sections, divisi, desks and individual players. It's a bit wow working like that - but I don't normally need to write that level of control. But it does sound great to me too.
The thing is this, with VSL's return policy, you don't have to trust anyone else's judgement but your own. I've had very little contact with the people at VSL, but when I have, they've been great. So if you buy from VSL directly, you will have the certainty that if you don't like it, VSL will either refund you, or swap the library out for one you do like. I don't think you can go too far wrong with that.
So go with your gut on this, in the knowledge that if you make a faux pas, unlike many other vendors, you won't get lumbered if you make an error in your selection.