I've been using it for quite a few years and i think with a quality post processor it is very easy and quick to get very usable G code. but,IMHO the drawback is that it does not offer a high degree of control over your toolpath.
Yes, Gibbscam can open native solidworks
Gibbscam is not a great CAD package. You will need a CAD package if you need quality prints. Shop floor style drawings are fine, but it is very limited.You can make solid models in gibbs if you have the 2.5d or Solidsurfacer packages.