After reading lots of threads here on earplugs, I thought I'd give 'em a try. I found some cheap-o foam ones for my commute ride today.
If you ride a commute, get some!
Some observations from the first use:
The good stuff:
1. The sound of the engine was so much "purr"-ier. Blocking out a lot of the grumbling loudness made it sound even smoother (and it already is quite smooth). Definitely an "Ahhhh..." moment there.
2. The wind noise was still there and noticeable (Even with a full-face helmet) but didn't whine as much. The top end was muted.
3. Less ambient noise, which doesn't matter as much for a commute ride, I'd wager, because I'm not cruisin' slow enjoying the scenery per se. I could still hear the traffic and such, but it was less of a distraction.
4. I felt more "dialed in"... i.e. my concentration seemed better. I remember reading someone state the same thing here on a thread about ear plugs... something about how the engine noise + wind noise causes our brains to shut down a level, making us slightly less aware and slightly more tired/spaced-out. I don't know if this is intrinsically true, but it seemed that way to me.
And the downsides:
Really only 1: they were a little uncomfortable at the end of the 25 minute ride. But I attribute that to them being the super-cheap-o kind of ear plugs... not even shaped... just foam cylinders. So getting some shaped foam, or even fancier ones, will likely remove that.
All in all, I'm a fan of 'em now, at least for my commute.