Without OT and prior to the IWR's there was more free time. I work a 221 schedule as do most controllers. Lets say your days off are Wednesday Thursday. You would work nights (3-11) on Friday and Saturday, then days (7-3) on Sunday and Monday, and last, Monday night for Tuesday you would work a mid (11-7). So ... Tuesday morning you would come off the mid and not have to be back at work till Friday at 3. That is a good amount of free time. Bang up sick on Friday and you can take a nice vacation ...
What happens now is with the scheduled 6 day weeks one of your days off becomes an OT, and since the scheduler is a management tool they pretty much screw you. 9 out of 10 times it's a Thursday evening OT shift or something that does not flow well.
One thing we can do is swap shifts. Lets say I got assigned a Thursday evening shift, and someone else has a day but wants a night. We can swap shifts.
Without OT the 221 schedule is really nice and gives a lot of free time away from work. With OT it's still not a bad schedule but the free time is not as good.
Hope the info helps.