If budget was no concern, I'd go with an adjustable desk like these...
AdjusTablesGeekDesk...coupled with a monitor arm:
ErgoTronThat way you can get the desk at the right height for keyboarding / mousing and your monitor at a comfortable eye level.
But, since I'm poor, I built my own keyboard tray using heavy duty drawer slides like these (props to Ripster for the link):
Lee Valley SlidesQuality drawer slides are strong enough that you can use a hefty piece of plywood that's wide enough for all your gear and won't wobble like crappy plastic trays do. I made my tray 32" wide and 18" deep, then covered the surface with a giant Ripper XXL mousepad cut to fit. Works great.
I guess I tend to lean on the desk fairly hard, but I never have found an arm-mounted ergo tray that wasn't wobbly and fiddly compared to a good solid drawer-slide tray. If you don't need adjustments like negative tilt, etc, then I really don't think the arm-mounted trays are a worthwhile investment.