I have been to Charleston Peak on Jan.29-30 this year. (only a week ago)
Couple of us hiked up SLT to the Charleston Peak.
The snow was hard packed and easy to go up with snowshoes with heal lifter or crampons.
On the way down, I switched my snowshoes to yaktrax. Because we got little bit of new fresh snow over the hard packed snow that makes no grip on snowshoes.
But, I rather use crampons if I brought it. Yaktrax was almost usuless at that condition.http://www.vegashikers.com/pic/20110129/p1.html
Anyway, there are another over month until Mid March and snow condition will be changed....or not....
But, If you are taking North Loop, I recommend to bring crampons. You better take Devil's Thumb shortcut to avoid steep hillside traverse.
I've been to Lee Peak on May 4th, last year.http://www.vegashikers.com/pic/20100504/p2.html
I made it to the Lee Peak without crampons, but I won't be able to make it farther without it.