I found 3S to be a decent little sampler. It plays samples on time, without pops, and it doesn't crash. If you're looking for a simple sampler that you can toss into a project easily and reliably, I'd definately recommend it.
Manytone's customer support was fantastic. The first reviewer gave it a "1", but I have a feeling that's just due to the review process here at kvr (e.g., if you haven't used customer service, then do you give it a 10, or leave it at 1? There's no way to not rate it.) I had a couple questions initially, and they were answered via email almost instantly...and it was a friday night even!
Ok, on to what I think could be improved:
1) It's limited to 4 samples per instrument. But hey, it is FREE and you can fire up as many instances as you want. More samples would mean fewer piano rolls, and easier to program velocity sensitive instruments.
2) I wish that MIDI note numbers were used instead of note names. 3S's "C1" did not match C1 in all of the applications that I tried. Not a real problem or anything, just confusing at first. I also found it a little bit tricky to select note names with the mouse.
Aside from those issues 3S is a great little sampler. Download it!!!!!