Yesterday I took along the Canon EF 135mm f2L lens with me to try it on the T2i. The 135L is one of my favourite lenses. Light, sharp, fast focusing, and has beautiful bokeh. It's a bit long to be used indoors, even with full frame, but outdoors, this lens really is versatile.
I shot mostly f2.2 to f2.8, just to give it a tad more depth of field, but the 135L can be used wide open without any issues. It's one of the sharpest lenses Canon has made. The T2i handled it extremely well. I am very surprised that this camera is far more accurate than previous Rebels, and even the 20D & 30D. It can obtain critical focus most of the time. Of course, this was done in broad day light. Have not tried the 135L in low light conditions.
I am very happy with the performance of the camera so far. In fact, this little camera grows on you after a while. The light weight, instant response, HD Video, beautiful LCD, fast focusing, and great image quality at low ISO, all combined into one nice package at a bargain price, compared to my original 300D back in 2003.
Ryan -- T2i & EF 135mm f2.0 L @ f2.2.
Dillon -- T2i & EF 135mm f2.0L @ f2.2. Larger Picture.
Oh my ear! -- T2i & EF 135mm f2.0L @ f4. Larger Picture.