I have minimal mileage with X3e and VSL, but I ran into no problems. I did upgrade to Platinum, and that too is working well with Vienna Instrument or Ensemble, right now I'm playing with VEPro, and again it's working pretty well.
It has been a while since I used Play - last time was when that had that Ghostwriter contest. That was the first version of Play on Windows that worked at all for me. The EW libraries do sound good, but I just don't need the headache of a new sample playback engine right now. In fact adding the VSL engine was a bit of a hurdle<G>.
The dry nature of the VSL instruments works for me, lots of control and flexibility, and they layer beautifully with the Cinesamples CineBrass and CineWinds, and 8Dio Adagietto and Agitato, and Chris Hein Horns. These are my core instruments in my template right now, and I do not feel like I am missing anything - most of the time.
If I had more confidence in the Play engine I'd probably add the Hollowood Strings, Brass and Winds for yet another take. I do have the original (GigaStudio) Quantum Leap Brass, and still use them from time to time.
I don't think there is much to worry about with VSL. There probably isn't a reason to worry about EW either, but they get just enough bad press for me to put that off for a bit longer.