I've got a Eheim ECCO model.

Pros

It has ZERO noise (I honestly don't know when it's running or not),
self priming with shutoff valves, basket design for media (i.e.
flexibility), easy to clean impler (sp?), can be CO2 injected. It has
dry runned for a couple hours without any damage (woops).

Cons

I've found that the intake line tends to compress at the canister.
Anyone have a fix for this? Like a shunt or something?
The cost, but worth it in the long run.

Greg