saw someone else with a book i'd left and she seemed to be online on her phone - expected to have that wild release caught too, but no result.
I've acquired a superstitious dread of watching my released books, or of looking for them if I drive by the spot - I've seen too many cases of people picking up the books, chatting excitedly about them, sometimes even mentioning BookCrossing ("I've heard of that, it's this web site where...") only to get no JEs on those books. Well, no *immediate* JEs; I've learned that many finders seem to prefer to wait until they've read a book to journal it (or perhaps they assume they're supposed to do it that way).
I do like to leave books on benches, especially those in scenic spots. If the weather's good I leave them without release-bags, so the little "I'm free" or "Traveling book" sticky-notes will flutter in the breeze and attract attention. And I do get a fair percentage of catches, so it seems to work for me.
Oh, and as for lukewarm or even negative reviews, I've had some really fun catches of books that I didn't like at all; either the finders like them anyway, or they enjoy the "traveling" idea more than the content of the book.