Have only rented once last summer (100-400, for taking baseball pics during high school season), from LensRentals.
Excellent experience, lens arrive in great shape, great pics.
One comment about them. When the lens arrived, I had taken it out of its case and placed the case in a "safe place, so I wouldn't mess it up". Kept the lens on the camera during the rental period. At the end, when I returned it, I had forgotten about the case and returned it without.
They emailed about the missing case, I emailed back, insisting that the lens had arrived without it, they said something about "flogging the mentally-lapsed employee" (joking, of course), but let it go at that and did not charge me for it. About 2 months later I found the lens case, returned it to them, apologizing profusely, they kindly thanked me for returning it.
Good, understanding, people. Would rent from them again.