Im looking for some feedback on how Dsp's have worked for you?

I've been looking in to the UAD-1, and I'm also wondering if there are any other well named or good qualiy dsp plugin bundles out there.

Does the load that it takes off the computer really make a big difference in the overall quality and sound. and are the plugins better do to the fact that they are not made to run of the host cpu, and are made to run off its own processing.