Okay, I'll go first.

How does the Impulse perform? I've seen them advertised on CCA's site and was thinking about one for my USP Tactical.

I think it works very well and is well made (not spot welded together). I only have about 200 rounds through it (I'm also using a USP Tactical) but it has had no stoppages. The level of suppression is good, I can shoot it without hearing protection and not get any ringing in my ears.
The September 2007 issue of Special Weapons magazine has an article comparing suppressors from Advanced Armament Corp (AAC), Knight's Armament Company (KAC) and Capital City Firearms (CCF). The levels of suppression given in their testing show all three being within two decibels of each other either wet or dry.

[suppression levels in decibels]
KAC. dry 22,wet 32
AAC. dry 21,wet 32
CCF. dry 20,wet 33

I only have a .22 suppressor now (Tactical Innovations Stratus) and LOVE IT!!! It doesn't have the highest sound reduction, but it still is very effective and I wanted the user disassembly feature as well. I've been shopping for a 45 ACP suppressor and would like to know some first hand experience with different cans.

The CCF might be what you're after, I've had mine apart for cleaning a few times, very simple.