The rule of thumb with modern tires is about 80% available traction from a clean, wet surface. I rode home in the rain yesterday and had no problems with the DL, stock tires and all.
Watch busy intersections because the oil never gets washed away. Stay in one of the car tire tracks and put your feet down carefully. Also watch out on other surfaces, like painted arrows, cobblestones, steel plates, etc. They can all be much more slippery when wet.
Keep your body dry with a good rain suit, boots, and gloves. Being cold is very distracting and tiring.
If you're still uncomfortable, don't ride in the rain. Get more practice on dry pavement and wait for a warm, rainy weekend day to take it easy and get used to the water.
06 DL-650 - SilverBlue
05 DL-650 - red (RIP - watch your mirrors!)