Epic makes an interesting point - nowadays very few reviews even mention bumps except to say, "not for..." Guess we don't ski bumps anymore.
I'll throw in two ideas 1) a ski that's really good on bumps will be light, for flinging, and have less sidecut and a more even flex pattern so you can drift/steer it and if you get in the backseat the ski won't automatically try to toss you. Go look at competition mogul skis to get the idea. Some folks think bump skis shouldn't have metal, but that's more about your own tendency to prang than bump performance.
2) All the posters who talk about how their stiff tailed, highly shaped skis "rip" bumps are talking more about their own expert abilities (or emotional commitments) than their ski's optimum. Yes, you can ski a SL in the bumps if you have really fast feet, excellent fore/aft control, and never need to skid or drift. Doesn't make it a bump ski, just means you're a great bump skier. My advice is to search for "forgiving" in description of any ski you plan to use a lot in bumps.
I ski NE, find my 6* are OK on hard bumps, mainly cuz of their quickness and moderate sidecut, but too heavy, stiff in the tail for real enjoyment. My Karmas are surprisingly good on softer, bigger bumps out west or after a snowfall back here, but not quick enough side to side for the front four at Stowe (or any double black bump run at Aspen). And I bought a pair of new Mantra's partly because I wanted a ski that could rock heavy snow in western bowls and still get through the bumps at the bottom, but I don't expect it to shine on KT-22. If I sound like I'm in the market for a better bump ski, I am...
So here are some demo suggestions that allow for eastern bumps with some all-mountain versatility. Note that none are the stiffest or highest performer of the brand. This is about bumps, not perfectly carved arcs:
1) Elan S12 - From what I hear on these threads and in reviews - only one of these I haven't skied yet - it's one perceived flaw (low energy) is a virtue in bumps and chop. Bet highest speed limit of these, 2nd best in crud. 2) Volkl 5*. Best all around eastern ski in the universe, bumps aren't a strength but not a weakness, either, and they'll eat up eastern ice. 4* is actually what Volkl recs for bumps. 3) Fischer RX6. Quicker and lighter than 5*, not as good in crud or at speed, but better in bumps, same on ice. My choice over the RX8 cuz it's a bit softer, less sidecut. 4) Dynastar Legend 8000 one notch shorter than you'd normally use. Just decent on ice, but rocks in any form of crud, crust, or pow, as good as the above in all but transparent razortooth moguls, and best choice for one ski if you have designs on getting out west. Warning: although very light, stiffest shovels and largest radii of the bunch, so bumps require positive steering/initiation. Thereafter really fun.
Last, I'd think hard about bindings. I've used Markers for 20 years and they're not the greatest in bumps (like to prerelease). That may/may not influence your thinking about 5* (think you can buy it flat). I like the pivot heel Looks a lot for bumps (old design, still best shock absorption in the universe, and safe) but hurry cuz they're leaving us. And Tyrolias look to have the best 21st century safety engineering (ACL's take a beating in bumps) plus decent shock absorption. Not a big fan of Salomons, although I sent my orthopedic surgeon's kid through college because of them.
Now you'll hear from left-out Atomic contigent, followed closely by wronged RX8 contigent and then we'll get back into the Great Marker debate...