A couple years ago I rode from Monterey back to the bay via the 1 in non-stop pelting crazy rain, and the SMH10 was rock solid. I recall listening to ridiculous 80s metal pretty much the whole way up the coast, which combined with the storm was pretty magical.
I have a 20S now, and while the first unit I got was a bit defective, the second replacement unit has been great and equally waterproof.
mine never leaves the helmet, except to charge, and I've been commuting with it (m-f, rain or shine) for about a year now.
The little golden pins that contact the base mounted to the helmet CAN get green, if you don't do a little maintenance on them. I clean everything up with a q tip and alcohol then douse with wd40 and reassemble.... seems to work fine :ride
Got rained on just about every day of a 3 week moto trip. Have ridden in rain numerous times since. My SMH10 is now about 2 years old and still works great.
I have the SMH10 for nearly two years now, used during every commute. Like everyone else has said, no issues at all in the rain. I charge mine about once a week. Be sure to close the rubber cover for the micro USB port and you'll be fine. I usually wipe out excess moisture near the pins when I get to my destination.
The only time I had an issue was human error, I rode to work in a monsoon and some water got into the charging port. I thought it was dry enough but it fried the unit when I charged it, whoops. Sena has amazing customer service, they emailed me postage and I had a new unit within a week.
SMH10R for the last year rain and shine! :thumbup never and issue.
Have a 10C now and love that thing. Have not had an issue yet with the exception of 1 video having pixelation. Will post a video of this mornings commute in the rain later.
As mentioned, just make sure the rubber flaps are closed. They have a little detent type feel when fully seated.
Mine currently has about 50k miles worth of use on it including numerous heavy rainstorms. So long as the USB connector cover is on good and tight it should be fine.
My 10C hasn't been in a nightmare storm but I use it every day and it definitely gets good and wet at times. No issues. I am super attentive though to making sure that the rubber port covers are fully closed and the mic/earphones connector is seated fully.