Pros- The expansion chamber is small, cheap and very efficient. Helps prevent inconsistent velocity, and Co2 Spikes. Built Tippmann tough. Easy to install. I see all these reviews saying that it is hard to install and they all seem to be on the model 98 or 98c. I think that their problems are not with the expansion chamber but with the vertical adapter.
Cons- Doesn't have the Co2 expansion capability of the larger expansion chambers.
I would recommend it to anyone planning on using Co2 in their gun.