I like open swim for my kids - it's in the evenings at the pool we use outside of their swim lessons, and it is the only time they'd get to swim with daddy. But for me, I won't swim unless it is lap swim. I don't abide people crossing the lanes and such, it is dangerous when you're swimming quickly! Pool etiquette is not something enough parents enforce with their kids and adults don't bother taking notice, which can make open swims hazardous for any serious working out.
Our lap swim is in the evening, there are some morning slots, too, but normally it's 5:30-7:30 pm at the local high school and that's awesome as far as I'm concerned. Open swim is after that