How warm is rando-race clothing?

At Vertfest last year, I was intrigued by the possibility of cutting a pound or more out of my gear by adopting clothing tactics from the race world. I'm willing to look goofy if it means I get to ski more.

How warm are ski-mo race tights compared with mid-weight softshells? Do they hold up to rain/sleet? Would I want warm pants in my pack as backup/survival gear on winter days?

I don't think a pound or two will make any difference in your performance, esp. if you are just carrying warm clothes in the pack in case you need them. Who know's, though? Try it...

At Vertfest last year, I was intrigued by the possibility of cutting a pound or more out of my gear by adopting clothing tactics from the race world. I'm willing to look goofy if it means I get to ski more.

How warm are ski-mo race tights compared with mid-weight softshells? Do they hold up to rain/sleet? Would I want warm pants in my pack as backup/survival gear on winter days?

You need to visit a website called "coldthistle". It's basically a gear geek blog by a local ice climber/skier called Dane.
Dane has a woody for skimo clothing and the blog talks about euro-trash( and now Wasatch)skimo freaks and weight weenie neurotics ad nauseam.
Do a search here.
coldthistle.blogspot.com/

Isn't one of the big advantages of a rando race suit is that since it is a "onesy" so you can't get snow down your butt?

C.A.M.P makes some interesting gear to help you keep from freezing on the descent portion -- including a wind breaker that you can put on without removing your pack,  www.camp-usa.com/products/apparel/flash-anorak-1446.asp

For myself the biggest drag on my uphill speed is the month's worth of emergency rations I carry on my waist and butt.

It's warm enough, and weather proof enough if you keep moving, the guys that are wearing race suits in the mountains are typically moving quickly, without stopping. Typically any backup gear is also minimal. Although the suits are lighter, the benefits aren't necessarily limited to weight;breathability, less fiddle factor, ease of skin storage etc. are more important features. If weight savings is the goal, bigger gains, or losses I should say, could be achieved through lighter skis, boots, bindings.

Not sure about the performance benefits, but you will look goofy.