good to know; thanks for the review! I've been considering renting some stuff from lens rentals but always wonder if it's worth the hassle ... or if I should just buy the lens 
I just buy the lens. Instead of renting for a few days, if there's a lens I am interested in trying, but not certain is the right lens for me, I watch my local Craiglist boards (quite active here), and buy the lens used. I won't pay more than 70% of the new price - that way, if I don't like it, I can sell it for little/no loss (and usually a small profit). I've done that with the 200/2.8L II, the 300/4L IS, 70-300 DO, and 24-105 (all bought then sold after a few months, although the 24-105 was an even exchange of selling the one bought used and buying the 5DII kit). I look on it as a long-term rental that's effectively free.
Most recently, I bought the EF 28-300mm f/3.5-5.6
L IS - used for less than 70% of then-current retail, and that was 3 days before the rebate ended and the retail price jumped $270.

Regarding lensrentals.com, I've heard nothing but good things about them, and I also really appreciate Roger Cicala's (the owner) contributions to the knowledge base about gear.