Link to a recent thread on this topic.
I think I probably for once have the most experience here for the question asked, a miracle on a US based forum for a guy from Aberdeen, Scotland.
I have skied at Whitefish in late March thru early April for over 30 days looking at my records tonight and it has everything. I've skied lots of powder and lots of corn in that timescale, you just don't know what you will get other than a fabulous welcome. On the 23rd March 2011 for example I was skiing 6-12" of fresh snow in bluebird skies and with a similar winter ahead things are looking good for my visit on the 21st and 22nd March 2012. I can't think of many days where I did not have fun or the snow was poor.
The benefit of late March is that Hellroaring is open until the 31st which has some wonderful terrain and great snow. The backside is mostly shorter runs but north facing so good skiing and the frontside for me is always good. Great long groomers and in powder or corn there is a helleva lot of good terrain to keep most people entertained for a week or more.
I've spoken about the Hibernation House in the other thread and the Alpinglow is now gone so thats my experience of staying on the mountain although I have a friend from back here who stayed in I believe the Morning Eagle complex but I may be wrong. I can ask him about that for you to be sure. My advice as before is that staying in town is a better bet for me and not having a car wont hurt you as the free bus I mentioned takes you up and down throughout the day.
Is the skiing worth it? Why do I go back.
If you want specifics fire away.