I've signed up for three different newsletters from Stack Exchange, each is received on an unique weekday. I learn a lot from other people's problems. The newsletters are far from the only emails I get, though, so plenty of time is spent in the inbox.
This would certainly be worth it if I found everything in the newsletters interesting, but there's often topics that are no use for me, like questions about Windows when I'm actually using Linux.
To minimize my (and others) time in the inbox I'd suggest:
- Combined newsletters (only the ones of choice, of course)
- Tag filters
- Reputation filters (sometimes the most popular questions aren't necessarily popular)
Good/bad idea? :-)