Interesting, the 'ole catch can or not debate. I belong to seven car forums, and every one has this same debate, with strong emotions on both sides.
For those of you who are running them and are happy campers, good on you.
For those who choose not do, great, for as Sir Duckferd posted (paraphrasing here), it will take thousands of miles to determine who was right to have one and who in hindsight would now have chosen run one from the beginning.
However, again my personal opinion that there are two other major factors that need to enter this debate, the kind of driving you are doing and whether you have been using Top Tier fuels. I am lucky, living in the country, take lots of long drives where my motor is up to temperature. About half of my mileage last year was road trips (14,000+ miles on four of them). Conversely, I have friends who are not retired, drive their cars 2-3 miles on their work commute, on the weekend running a lot of short errands -- and their motors spend a majority of their trips not even up to temperature. Keeping the valves hot (engine of full operating temp) is one key way to burn off all forms of crap including gasoline vapors. And of course using Top Tier fuels has been repeatedly proven to not only give us better fuel mileage, and using Top Tier fuels also results in cleaner motor insides.
One GM engineer's comment is, I believe, is worth repeating. He is powertrain engineer, works on the 455+ HP Corvette, Camaro and Cadillac's -- many of those motors now in the 640+ HP/640 TQ range, when he sarcastically answered a question of how come GM does not run catch cans (except in the track Z28's), and he said, "don't you think if GM felt it necessary to run a $20 catch can, we would be doing that?" I am guessing that the $20 figure would be GM's actual cost if a catch can were factory installed as part of the assembly line process.
Let the strong opinions on all sides continue, and I bet if I were on seven more car forums, I would fine seven more threads with differences of opinion as to whether catch cans are necessary or not.
In this case, oil quality makes a bigger difference. At least if you're in the US, where our fuel is mostly homogenous except for some additive packs. But generally you're at the mercy of the powertrain engineers and how carefully they tuned their system to work under any condition.
You *do* want to run the engine warm, as this burns off moisture in the oil. One issue that occurred in the past with the Northern areas is that as cars are sitting at the dealership, being moved from one end of the lot to the other in order to plow the lot, you sometimes had engine failures because so much water accumulated in the oil pan from the short run times that it caused slush to clog the oil pickup tube.
It's debatable whether PCV catch cans make a difference in port injected engines, because at that point you're mostly concerned about killing the catalytic converter/doing very poorly in emissions testing (by the way, the cost would be more like a couple of bucks since they integrate these "catch can" systems into the valve cover or internally into the engine). If you're a performance engineer, you'd be worried about certain corners feeding oil directly into the PCV outlet and getting sucked into the engine.
Oil separation has become extremely important since direct injection came out. Even more so in high blowby engines (turbocharged), where they've started resembling science projects with their swirl vortex generators and centrifuges, etc. The thing is though, newer generation engines have already improved this aspect of their engine design, about 20x since the ~2008 time period when the Germans and Koreans found out the hard way that you can't just add direct injection and not consider other aspects of your system design. It's gotten so good that catch cans nowadays are mostly catching fuel and water, not actual oil.