Entering the dSLR world with a Canon XTI.
I am very interested in taking landscape shots for a long trip ahead.
So, I am concerned about dropping around $630 for the Canon EF-S 10-22mm lens (in addition to the camera, accessories and another lens) if in the future it cant be used if I do upgrade my camera to one with full-frame sensor or something that wont use the EF-S lens.
I have read the reviews regarding the sigma, tokina equivalent which according to www.the-digital-picture.com
(i think) are slightly inferior, however at my level would these be better options?
pardon my ignorance.
what are your opinions?

And still great IQ. Quite comparable to the 10-22. Remember, %98.76 of statistics are wrong and something on paper is just something on paper. 
