They are beautiful things, we've had a DSP4000 and 7000 in the studio but as computing power increases they'll become less useful, expect the prices to drop dramatically in the next couple of years for the older models as more quality pitch shift tools and stuff are available for native systems.

On the other hand there are some surreal reverbs to be had and if you fancy an outboard effects processor that does something other than boring bread and butter effects they are absolutely the bomb.

you can design new effects on the PC and dump them to the device over a serial connection as well.

Ours lives pretty much 90% of the time on a patch that makes pop vocals sound big and warm but when it gets used for something else it shines in the mix.