From the reading I've done, most experts, sites, etc. seem to say that pellets are unnecessary, though if your bunny is on the skinny side it might be a good idea to feed limited pellets. I give both my bunnies a handful a day, which amounts to a smaller portion for Kiwi (6.4 pounds), who's of completely normal weight, and a larger portion for the smaller Coco (4.2 pounds) who's of a healthy weight but on the skinnier side.
I think the bottom line is:
1. Hay is ABSOLUTELY NECESSARY, and there's no such thing as too much if you're feeding timothy hay, orchard grass, etc. with the exception of alfalfa. Alfalfa should only be fed in small quantities or not at all to adult bunnies. It's good for them while they're babies, I hear, though. It's higher in calories and protein is the reason, and I guess growing rabbits benefit from that, whereas for the grown-ups it's not so good.
2. A couple to a few servings of fresh veggies daily and the occasional small piece of fruit is also important. Some good picks: dandelion greens and flowers, Romaine lettuce, celery, cilantro, parsley, endive.
3. Pellets in small quantities or not at all. I think pellets are seen as necessary by people who don't realize that rabbits are better off on a diet of hay and vegetables, and by people who think vegetables are bad for rabbits (I've encountered some of these online; people who think all lettuce or leafy greens are a no-no, which couldn't be farther from the truth! Iceberg lettuce is no good, but my bunnies love Romaine, escarole, endive, etc.).