It can be done.
We're using healing surges. However, the use of healing surges has promted us to switch over to a homebrewed variant of Vitality and Wound Points (similar to what's in Unearthed Arcana). Healing surges replenish vitality, but do nothing for wounds. Magical healing, though, relies on healing surges, too. A character must have a healing surge in order to have wounds healed through magical means. No healing surge, and magic can only heal vitality points.
I haven't tried rituals, yet. But, it's on the list. Was on the list even before
4E came out (incantations, I think it was called).
We've imported stuff piecemeal from Pathfinder & the Books of Experimental Might, too. And, we use Arcana Evolved side-by-side with the regular 3.5 classes. However, we don't use any prestige classes (we use prestige feats, instead). And, when multiclassing; BAB, Hit Dice, and saves don't stack. The character simply gets the best total of each class (similar to gestalt, but advancement is only one class at a time).
I want to try adding
4E's marks to 3.X, but I haven't decided how, yet. I'll probably do it when I get around to re-writing the Marshal and/or writing up a 3.x Warlord. Though, I'm not convince that a Warlord needs to be a separate class from the fighter in 3.x. Warlordish feats may be the route that I go (but, maybe not).
We, also, did away with default iterative attacks for all classes other than the Monk and Oathsworn. Other classes may purchase extra attacks through feats. However, all classes get a base damage & defense bonus (both of which vary by class).
But, to answer your question, I think there's a lot in
4E that can be used in a 3.x game. For example, my monsters have picked up a few
4E abilities. Kobolds, for example, are Shifty (able to take two 5' steps per round, instead of one).