The Tamron 28-75 was my first 'serious' lens that I bought. Sporting a fixed f/2.8 aperture, a great focal range, and spectacular optics for the price, it was my most-used lens. For me, the focal range makes for a great portraiture lens, walk-around (although perhaps a bit long sometimes on a 1.6x crop body like your XTi), and just a plain ol' fun lens.
I just ordered a 24-70L a couple days ago, so I will be parting with my beloved Tamron. If you're interested in this lens (sharp copy, can provide samples) PM me and we can work out a deal. I also have a Hoya S-HMC Pro1 67mm UV filter on this lens that has been on since day 1 that I will include.
Happy shooting!
~Travis