Depends on traffic and road conditions. When the rain first starts the oil and stuff on the roads can get real slippery. 15-20 minutes of good hard rain washes them off.
Straight road, no traffic, 60 MPH and I stay almost dry in a fairly hard rain.
Rain at night, the biggest concern is visibility. Seeing and being seen. Rode 50 miles last Saturday night in the rain. Almost no traffic, I could barely see the lines painted on the roads especially if a car was coming towards us, I lead the group at 45-50MPH hoping a car would pass us so I could follow the tail lights.

 

Appolutely. Been awhile back but I was going with the flow of traffic in rain that had just started and some dipstick cut me off. Rear brake locked up I ended up almost sideways for about 200'. Looked in my mirror when I got straighten out and all traffic behind was about pretty stopped waiting to see if would go boom.

 

Riding home from work a storm started brewing, 35 or so mile an hour wind. Trying to beat the rain when a LEO pulled behind me. I drove 20 miles with the LEO behind me. When I stopped at the light he pulled up beside me cause I was turning left, rolled his windows down and told me he was worried about me riding with my wife and wanted to give me an escort but he couldn't go any further I thanked him and proceeded to turn. I got about two miles from the house and it got dark, I was wearing an helmet with rain pouring down when i hit a piece of tree that had fell in the road could thing it was rotten but what a shock.

My two cents slow down so you can see clearly and react accordingly.

 

While in Idaho I learned that riding at highway speeds helped to keep the bike upright when there was a thin layer of water sheeting on the road. Riding here we often have showers on the windward sides of the islands (some towns can get up to 200 INCHES of rain in a year) or up in the mountains. The regular rains seem to help keep the oil off the roads but I look out for leaves, mud, or sand. I think I read that a bike with good tires has about 80% of its normal traction when it is raining. If you are on a painted surface (intersections and divider lines) I think that you will find more traction on an ice rink (I have tried to ride on lake Michigan when it was frozen- IN MY YOUNGER/DUMBER YEARS). It seems to be a situation where you should try to stay on clear pavement and pay attention to how the bike "FEELS". Avoiding puddles is really good because you never know how deep of a hole they are hiding.

Beside that, have fun when you get a free bike wash!

 

I usualy pull off under a over pass when the rain first starts, I wait about an hour so the roads have time to wash off the slick stuff. Then I go with the flow of traffic. Unles your in CA in which case you better get off and stay put. Those guys in SO Cal will start banging in to each other if they even smell rain.

 

One thing to be especially carefull of is new tires in rain. I got a fresh set of tires on my RKC and got caught in the rain shortly after. Coming out of a turn at on on-ramp I hit a slight berm in the asphalt which caused the front end to jump a little. That's all it took to cause the front tire to slide out from the road. I got lucky and saved it but if another car had been around you would have been reading about the greasy spot in the road beside the wrecked bike.