I wear Pearl Izumi Amphib tights with knee warmers and lycra shorts underneath. It may be a little under dressed, but I sure do get hot in a hurry. My main concern isn't my legs, but my knees. I'm skin and bones, so I have to keep my knobby knees covered.

The amfibs have that water panel that makes a great windbreaker, too.

I've been wearing cargo pants, as I like being able to put everything into the pockets (lights, batteries, keys, etc.). When I get to the office and change into work clothes everything stays in the cargo pants pockets and is ready for the ride home. Am thinking about getting a pair of cargo pants with the 'zip off" legs so I can use them when the weather warms up.

not a popular choice but one I've been real happy with so far this winter...
Running tights, with or without knee warmers, under Carhart double knee jeans. So far, this combo has been great down to about 5 degrees and riding in snow. I do wash the jeans with nik-wax product so thats my disclaimer. No jeans in rain. I have goretex over pants for that...

Old Columbia BugaBoo shell system for cold/wet, and a nik waxed Nike running jacket for dry down to about 15F....

Hope that helps...Mostly multipurpose equipment. Have a hard time swallowing the prices' of bike specific gear...

Sometimes I wear just my Dickies jeans or cargo pants when I ride because my legs heat up quicker than anything else, and I just deal with the chill early on. Because it rains in the Puget Sound so much, I picked up an inexpensive pair of nylon outer pants for soccer, I think (with zip bottom legs to take off while still wearing shoes) at a thrift store to keep wind and light rain away. It works really well. I do not get cold at all in that department. Because rain is such an issue, I am really eying a hundred dollar pair of rain cycling commuter pants that would be good enough to wear on their own (to the pub or school) as well as as an over layer for more work-orientated things.

I wear long underwear that is appropriate for the season, my work pants (dress slacks), and gaitors.

The gaitors keep my legs warm and keep my pants clean.

When I get to work, a tug on the gaitors and off they come. In seconds, I am walking to down the hallway clean and comfortable with my helmut, gaitors and gloves under my arm looking professional and saying good-morning to the colleagues.

Yet another vote for the REI Novara Headwind pants ...