Wow, I'm an idiot. I didn't even see what you guys were saying about conflicting trips! Sorry about that. But you are correct that PBS will not award a trip that conflicts with other events on your schedule and your ability to swap will be greatly reduced. You have to consider, though, that PBS is one giant initial open time pot where you are more likely to get what you want the first time around and not have to swap later. If PBS awards you a few 2 days and a few 4 days, you'll only have to worry about swapping a few trips instead of the whole month. If you were awarded a line under line bidding with ALL 4 days and tried to swap out with the conflict trips that dropped into open time, your success would be rather low because of ASA's "red arrow day" conflicts. I actually prefer the PBS conflict feature, and here is why:

I like to work Monday through Thursday commutable 4 days. Next month, I have AQP that runs Wednesday through Saturday. Had we still been using the line bidding system, I would have been awarded a 4 day on the same week that I have AQP. The Wednesday and Thursday portion would have dropped into open time, but I'd still be left with a 2 day on Monday and Tuesday which would have made for 6 days of work in a row. No thank you!

With PBS, I just elected to not bid ANY trips the week of my AQP. Now I work a 3 day Mon-Wed during the first week of February, and then don't go back to work until the following Wednesday for AQP. That gives me 6 days off that I would not have had under line bidding. After AQP, I resume my normal weekends off, commutable trips. I was able to get a 3 day starting Tuesday after AQP, so I have 2 days off between training and flying and still get 3 days off the following weekend. To clarify, my schedule is like this:

3 on, 6 off, 4 AQP, 2 off, 3 on, 3, off, 4 on, 3 off, 4 on