You may want to consider a chemical water treatment if you are really looking to shave ounces. Although I do like and sometimes use my filter, I generally go with PolarPure iodine (crystals in a small jar) -it weighs about 3 oz. empty, and you fill it up with streamwater to make a solution, then put 2 capfuls per quart of water. It does have a shortcoming or two (taste being foremost in most people's minds), but I've been using the stuff for so long that for me, the taste of iodine equals refreshment. Plus it never breaks or clogs, and one little bottle is good for something like 5000 quarts.
There are also other alternatives like Potable Aqua.
Eliminate all bowls and plates except for a lexan spoon. You can eat out of the pot or the food bag.
I also like to listen to music/books while I hike, so my weight splurge has recently been my iPod and a Solio solar charger, which works like a dream.
Tents are also unnecessary. The truly hardcore ultralight hikers I know generally use some kind of tyvek or sill nylon tarp and just bring a few extra ounces of deet. Plus it rarely rains at night in the Sierras.
I'm loving this discussion, and although I'm considering going full ultralight for the JMT in a couple weeks, I don't think my Go Lite Jam 2 can accomodate a bear canister and 10 days worth of food (for the Vermillion Valley-Kearsarge Pass section) plus all my gear. Sticking to my huge, heavier Dana Designs pack. It does make it significantly easier for long haul hikes to carry 20-25 lbs. vs. 40-45, but I like being a badass. Plus, hiking 15 miles a day with a full pack for 3 weeks turns you in to a machine. Lungs and legs, baby!!!