I've been reading into this for the past 2 weeks off and on. They are very useful if you do alot of high revving stuff, even if you don't they are good insurance.
I was going to fork out roughly $200 for the Provent 200, but I've decided on one of the cheaper eBay ones (haven't got anything yet).
People buy the cheap eBay cans and put stainless steel wool/scrubber type stuff in them to help with trapping the oil. I've thought about this.
What happens if some or part of this material becomes loose, it's going to get sucked into your turbo. For that reason, I don't think I'll be putting anything in my eBay catch can.
I was also concerned about the venting on cans like the Provent, that is a possible point of ingress for water into your intake.