My "L" lens buying spree included the purchase of the Canon L 135mm F2. After having lurked on this forum and using it for helping me make buying decisions, I have decided to post my thoughts on this incredible lens.
First off, let me say that I've been blessed with all of my lens purchases. After reading here, I know it is possible to get a bad copy of a lens, but all of the lenses that I own are wonderful. I've had no major problems with any of them. You get what you pay for in any lens purchase. I will admit that I'm now quite fond of the L series. My 50mm 1.4 and my 85mm 1.8 are fast, and I'm more comfortable using primes than I am zooms, because of how well they hande low light situations.
Let's talk about the 135 L. It's sharp, clear, bright. Autofocus is quick, smooth, and I was blown away by the colors that the L lens provided. Photos almost look 3D. My copy is sharp at F2, as well, no softness noticed in the corners. The lens is built well, feels solid, and the bokeh on wide open shots is almost dream like. Because of this, I've become more keen on my choice of backgrounds for the photographs I make. The price was good, and since I don't need a super long lens, feel that this lens rounded out my collection. I also own the big brother, the 200MM F2.8 L. I will probably look at purchasing the 24-105MM when it comes out, but only after reading and studying the reviews here. I like the convenience of the zoom, but I'm still stuck on a good fast prime lens. They are hard to stay away from!