A few weeks ago I bought a NiteRider Sol from REI (they had it on sale for Labor Day). I did my first longish ride in the rain this past Thursday night, and the light died on me about 15 minutes from home. I stopped, fiddled with it, got it work again, then it died again, I got it back on... and so forth. When I actually got home it was working, but wouldn't turn off. Being tired and somewhat buzzed at the time, I unplugged it, left the battery out to dry, and then plugged it in the next morning to charge. When I got home the following evening the light only kind-of sort-of worked; I could get it flicker to life for a few seconds, then it would die again. I think the button may have shorted out in the rain.
Before it died, I liked the Sol due to the small size of its lamp, and rather impressive brightness for its size, in addition to its run time. The fact that it died so quickly leaves a rather bad impression though.
I upgraded to a CygoLite DualCross 300 when I returned the Sol to REI. I tried it last night for a short ride to a cafe and the light itself is bigger, bulkier, has a bigger battery that is more difficult to mount, with a cord that is too long, but is definitely a better light. Brighter beam, larger surface area, very easy to see by. It was sprinkling last night, so I haven't really tested it in the rain yet, but I probably will this week as the club I've started riding with rides rain or no two times a week.