I own a fair amount of orchestral libraries that I use everyday. I have been following VSL for years, I'm a big fan of the Dimension series more particularly. I immediately set out to buy everything Synchron because like many others I expected VSL to do wonders with wet samples.
I will probably echo a lot of what has already been said here and elsewhere. The quality of the recordings is stunning. High definition, low noise floor, the hall translates beautifully, almost no room adding up or phase issues. I'm very impressed with Synchron Percussion, FX Strings I and the Yamaha CFX, both in terms of sound and playability.
In my view, Synchron Strings I fall short for the same reasons the Percussion and Yamaha work so nicely: on a one instrument = one sound scenario, precision, clarity and timing are key. Not so much when you record an ensemble of players, who would not perform so surgically in live conditions. Hence their sounding a bit thin and sterile to me, especially the long notes.
The legato transitions feel a bit jerky, I also find the layered sforzandos disappointing, and the absence of a portamento unjustifiable for the first instalment of a string library. And who needs a 12s (shortest) to 30s (longest) crescendo/diminuendo? It's nice to have them as a bonus, but they should not be our only option, it doesn't make sense in a day to day, practical basis.
I more generally think it is a pity VSL didn't go the same 'organic' route with Synchron Strings I as they did with the gorgeous FX Strings I. The two don't blend too well for the same reason by the way, which certainly feels counter productive. I find the mid mics a bit reedy and difficult to mix too, I haven't yet been able to EQ them to taste.
I managed things with Dimension Strings that I couldn’t achieve with any other libraries as far as realism goes. Synchron Strings I is still in its infancy, and I sincerely hope the VSL team makes them better, because they very well know how. Congratulations on the rest of the Synchron line!