Here is my super hastily written lens review: This is the lens I rented this past weekend kind of on a whim at the last minute - the Canon 24 mm f3.5 L tilt shift lens. I didn't really have much time to read about it, but since I had three days off I thought it was a good time to try it out. What I did read about it said the learning curve on it was steep. I would agree. I would suggest reading about them more if you just plan to rent one for a few days.
You need to have plenty of time to use it and then have plenty of time to review what you made with it and time to go back and try again---more time than you would have in a super busy 3 day weekend. I had rented the 45 mm tilt shift back in October and ended up keeping it for a week. That lens was easier to use it seemed than the 24. It seemed like I could tell from the LCD pretty much what was getting without magnifying the image. With the 24, it still seemed a mystery even when magnifying the image on the LCD. Oh, this is where I should say I am not trying to take photos of buildings which is what the tilt shift is usually used for I think, but of people. I want to get in focus faces and blurry dresses, buildings behind the people, etc. I was able to get that with the 45. I just think with the 24 I need more practice. Okay, one more thing, when I rented the lens, the guy at the counter asked me if I knew how to use it and I said yes, cuz I thought it would be like the 24. I wish I had said No and then heard whatever he had to say. The shift dial was realllllly tight on the lens and so I didn't want to break it, so I think I only used the tilt part. Or vice versa, not sure. Either way, I did not experience the full functionality of the lens cuz I was afraid of breaking it and owing the store something like 1600 bucks, which is about the price I have seen for it online. So if you go to Tempe Camera and rent this lens, get them to show you the tilt and shift and make sure that you are comfortable with turning the knobs and don't feel like you are going to destroy the little lens (and therefore kind of waste your money like I did.)
I would like to rent it again, but since weekend rentals add up so quickly and week rentals are so expensive, I think it just makes sense not to and for me and save up and buy a lens baby because I would really love to try one of those. I think I would get some of the effects I am after with a lens baby.