Personally, I don't like to use them. They can wreak havoc with your mix. Onstage is a different story, but when mixing, I find it difficult to get predictible results. If you needed a super-quick fix for a bad recording, it'd probably do wonders. In my opinion, I don't think they belong in the studio.
I usually stay away from harmonic exciters. I try to nail the tone during tracking. If the result is pleasing though, and it is not difficult to listen to due to phase distortion, do what you want.
Hold on a sec - I just looked it up, and isn't at all what I had in mind. That thing looks like some kind of quasi-mastering / possibly strange effect plugin. As well, I thought Arboretum had a decent reputation.
arboretum makes a PC one too...these things work great *AS FX *
dont try and use them to correct something, theyll do funny phase stuff, but to put a firecracker on the snare drum, the DSP FX Aural Exciter and the BBE among others can do fun stuff, just check mono every once in a while cuz like seanmorse says, they can do funny stuff