It also helps warm up the soil. We use no till "lasagne" style gardening in raised beds and I have nothing but great things to say about it.
Denny, you like the lasagna gardening method huh? I bought that book early summer and plan on doing some of that this coming year. I've been collecting materials to help make my layers. Sounds like a neat idea. I really like that hugelkulture method too. It makes a ton of sense, although we don't have a lot of forest for dead trees around here. However, I do have one large tree in my yard that is dead from the drought and ensuing bugs. I may start taking it apart to make one.
In many places around here, you can just put seeds in dirt and they'll grow, so it kind of bugs me that the "experts" act like raised beds are required for everybody. I think it deters people from getting into gardening, because it sounds like too much work. I've had vegetable gardens at 3 different houses, two in Spokane and one on San Juan Island, and I've never used raised beds. The nice thing about not using raised beds is you can just rototill the whole garden for a nice clean slate in the Spring. Throw in a truckload of manure and the previous year's compost to build up the soil and you're good. People with clay or extremely rocky soil will benefit greatly from raised beds, but I have no interest in building them for my garden. Those hoop-houses of Denny's, on the other hand, look tempting. Are those anchored with rebar pounded into the ground? Is the white material just regular PVC or is it water supply hose?
Supposedly the lasagna method eliminates this. You just keep adding layers of different mediums and it builds a raised bed and no tilling or digging is required. I'm still studying this method as I'v always been a fan of tilling the crap out of a place while adding lots of new stuff to build it up.