A few things have changed since I first wrote about how treasure is presented in my upcoming 4e fanzine. The main development is simple; I am now completely sold on inherent bonuses. The zine is all high Paragon and Epic tier, so I was ready to just roll with +5 and +6 items, but now I have just completely stripped "plusses" altogether. Everything else is pretty much the same: no prices or rarity for items, few items for sale, narrative descriptions of items as opposed to stat blocks, etc. There are however a few new wrinkles that I thought I would share. I probably should call them "old wrinkles", because these rules hearken back to the classic editions.
First, some items will have charges. I think this is a much better way to deal with powerful items as opposed to item rarity. I particularly dislike the concept of "rare" items, items supposedly so interesting that you don't mind playing 10 levels with the thing. I am sorry, I am in the process of wrapping up a 4e campaign that took almost 2 years to get through 10 levels. You can't tell me it would be fun to use the same sword for that long a stretch, even if it gives you foot rubs and cooks you Filet Mignon every night. Items with charges are a much cooler way to introduce powerful items into your game; they have a built in "self-destruct" button, a fail safe that makes sure they don't last forever. For example, I might have a staff that automatically crits whenever it hits. Super-powerful. Not something you want in the game for very long, but tolerable if it is limited to a few charges. Of course, don't tell the recipient how many charges it has, that adds to the fun (the DM could roll a d6 or d8 and track separately).
Second, we get away from telling players an item's properties right off the bat. Require them to use the item to find out. This was how you could get a PC to use a cursed item or drink poison back in the day. If they find a potion, they have to take a tiny sip to know what it does (this doesn't waste the potion). Is it dickish to poison your PCs, or to give out cursed weapons? Hell no. It's tradition. It is flavorful. You don't do it every time, or even often, but in rare instances it is totally within the bounds of fair play. In fact, I always remember cursed items as actually adding a lot of fun to the sessions they appeared in.
So that's it. Nothing too groundbreaking. If you hate item rarity as much as I do, yet still want to use powerful items in your 4e games, try items with charges. Also consider requiring the PCs to use trial and error to find out the properties of their items. Oh, and poison them every once and a while.