At first I was turned off by the reviews for Solo Violin, but after purchasing I'm really satisfied. It doesn't sound like a real violin, but that's not really my goal, but instead to leave an authentic impression to the ears of the people I work with, and most of all to have fun playing the thing on my keyboard. I can get a really smooth non-vibrato to vibrato transition.
For the most part I like Solo Cello. All of the samples are spot on... but the problem I'm having is that it doesn't have an xfade patch with slurring like Solo Violin did. I was looking forward to the download because I wanted to practice that same technique, but now I'm considering resampling the samples into my copy of Reason or Kontakt because I can't get the patch I'd like to play with, and then you don't get the slurring that the play sampler has to offer, or the nice reverbs.
So that's a feature request I guess. It really shouldn't be too hard to program it in...then again maybe there's a way to do it in the PLAY engine or using the PLAY engine in conjuction with a DAW? I'm not sure...