Fresh snow is key. I've ridden mid-day snow lots of times, but you have to get off the street to ride it. We used to ride LRT at night (c. '89-'91), from like 2am to 4am. When there's snow and a biggish moon you almost don't need lights, esp after 30 min out there. I ride downtown mostly in the alleys at night. I ride Landon during the day, or I ride over the river and take the levy either East or West. You'd be surprised how much traffic those things get when you can see who and what have been walking on it.
Before the expanded that paved trail from the theaters to Clinton, and when we lived there, I used to ride and rollerblade it w/ my daughter. It was near our house. Great memories there, but if you're making the trip, you might as well ride Clinton or LRT. I'd sugges LRT 'most every time when those are the choices. If you're going to be in and out, and if you want technical (think the Govs w/ rocks), go Clinton. If you want to hit FSB or grab a slice (@Johnnie's/Rudy's/Papa Keno's), you'd be best to go to LRT. Before we moved here we lived right by Lied Ctr, and there were all sorts of little trails around there. Nothing big, but kind of fun when you wanted to cut through from 23rd to 15th, which was how we'd come home from the theaters out on the South end of Iowa.
If it snows, and school's cancelled, I'M riding. I'm not even changing tires. I'm just going to be frustrated w/ the slipping if we go to the trail. We can take Landon/Shunga out East and around to catch Wittenberg, and backdoor into Dornwood and ride some of that then bring it on back home; West on 25th to Landon, to my house. If school isn't cancelled (I'm giving finals), bundle up boys and girls, but enjoy it without me.