"Ultralight tripod" can be an oxymoron. The main reason you have a monopod or tripod is to stabilize the camera. A monopod is better than hand held, especially with a long lens (>200). A tripod is much better than a monopod, but just because it has three feet on the ground doesn't mean it's stable.
If you're shooting outdoors, you likely will have to deal with wind and/or uneven ground. With DSLR cameras, even the movement of the camera mirror can cause vibration that can make the photo less sharp (that's why you should use a cable release and mirror up mode for shooting on a tripod). If that small of a vibration can affect the quality of your photo, then much more so wind and uneven ground.
Most ultralight tripods and self-rigged "solutions" such as trekking poles simply won't cut it with the setup you have. The 40D plus 10-22 weighs about 3 pounds. You need something more stable and something that's not going to fall or blow over and ruin $1500 worth of equipment.
While a stable tripod is less needed with an ultra-wide angle lens, you may not want to limit your future lens choices by getting a lightweight pod that only will be effective with an ultra-wide lens. I do a lot of nature and landscape photography, and most of my best shots are with medium and long telephotos.
Gitzo is top of the line and very expensive. I recommend you consider Feisol tripods (www.feisol.net). Feisol sells some nice carbon tripods that weigh just over 2 lbs for around $300. You also should consider a good ballhead, such as the Markins Q3 (0.8 lbs) or M-10 (1.1 lbs). Manfrotto/Bogen also has some lightweight carbon and aluminum tripods.
If you're serious about nature/landscape photography, buy a good tripod and ballhead. This is one piece of equipment where quality counts more than ounces. You won't regret it.