I'm with fahl5 on this - the Synchron Player works so differently than VI or VI Pro that few of us have sufficient experience yet to express a deeply informed opinion as to the library's ultimate quality.
Nevertheless, here's my shallow opinion: There's a dramatic improvement between my first Synchon Strings project in its original VI version and the rebuilt project using Synchron Player. Legato is much smoother; releases, which were particularly squirrely in VIP, are a non-issue now. It was no fun re-doing all the keyswitches, but in the end there were far fewer of them. I love having real-time control over vibrato; I love not mucking around with repetition samples, like the other VSL string libraries require.
So, my very premature opinion, based on one soft, lyrical piece, is that Synchron Strings is a major advance over previous VSL string libraries - enough of an advance that I'd classify it as "almost meets expectations." But I may modify that view when some piece requires a nice light spiccato, or relies heavily on sforzato, which I agree with others sounds pretty unconvincing.
Any change as radical as this one is bound to be accompanied by some missteps - and VSL has made things much worse with this library's piecemeal and agonizingly slow roll-out. Besides the near-nonfunctionality of the original version, there are now the countless hours people will have to spend porting their Synchron Strings sequences from VI/VI Pro to Synchron Player. Selling the library at full price before the player was ready created a vast pool of ill-will that's going to be hard to overcome.
--Mark Arnest