I own 3 pairs.
1. Craft brand half tights with windproof material in the crotch. Can't remember the exact model and I'm too lazy to go dig them out of winter gear storage. I pretty much only wear these on subzero windchill days. They are pretty short (only go halfway down my thigh) so I've never worn them without something else over them. But I recommend them if you plan to encounter that kind of weather.
2. The most basic Nike half tights. The ones you can get for ~$40 at your local running store. They don't have any pockets which is annoying, but otherwise I like them quite a bit. They are comfortable and perfect for those 35-50 degree spring/fall days.
3. Tracksmith reggie tights. LR seems to have a love/hate relationship with Tracksmith for legitimate reasons, but for tights and shorts I think they make good stuff. They are probably a little warmer than my Nike ones (more nylon) and have a roomy pocket in back which is nice.
All three have been good purchases I would say. I only regret that it took me about 15 years of running in the northern midwest to discover the joys of half tights.