My first rental from BorrowLenses.com went off without a hitch. I'm local so I took advantage of the local pickup option and rented a Canon 10-22mm wide angle lens and a 60mm macro lens for a trip. Pickup was fast- I walked in, showed my ID, signed a form and away I went. Returning the lenses was just as easy.
The only downside of BorrowLenses.com that I can see is the opportunity to use, and fall in love with, lenses that I can't really afford.