Anyone had any firsthand experience with different tires and tread design used for daily riding on wet pavement?  My 06 S40 has the original tires but it's raining again in the Seattle area and am a bit hesitant to venture out on in these conditions.

I agree, standard tires will work just fine in the wet conditions.

Watch out that tar strips, paint, and metal gratings (sewer covers and the like) are all much more slick in the rain. Runoff can also cause rocks/gravel/pebbles to collect which act like little ball bearings.

If you don't try anything too crazy (none of that knee scraping!) it'll be just fine.

not meaning to add to the negatives, but your front brake might get a little weaker, your belt might squeak, your brakes might squeal, and depending on how your bike is jetted, it might act a little different, but it isn't bad.

now, trying to drive through a puddle that comes up higher than your exhaust pipe... don't do that. I mistook a miniature lake in the road for a slightly wet spot and ended up getting enough water in my bike to kill it and make the oil go all funky. ... I also had a pod filter during that adventure out and about in the worst rainstorm in a few years so that didn't help keep water out of the engine...

I feel like I'd get run down at 10-15mph under the limit.

I usually slow down more than I typically do around turns (so 10-15 over instead of 20-25) and I apply the brakes much earlier. Then again, most of my commute is 25mph zones, so 10-15 over isn't so much.

If you're on a 75mph highway though... I'd find an underpass. Hydroplaning would not be fun. and that rain can sting!