I got a 25K to Vegas a while back with no problems at all on US. I'm looking at some other 25K awards for this summer and they're available, albeit a little restricted now. They were more open a few weeks ago.
An alternate is to go through LAX (which can't always be pulled off online) or to go to LAX and get a (currently) $58 r/t to LAS, on WN, UA/Ted, or someone else that's supporting that route.