I hated full synch. That was BS and usually just made the mission needlessly frustrating and not more interesting.
I hated full synch also. Can't tell you how many times I had to replay that goddamn tank mission to get it.
The timed ones were annoying too. I'd pretty much have to always do them twice, once to thoroughly explore and make sure I found all the flags etc. and then a second time to beat the timer.