I don't buy often, but I did buy a year of QT after a month of submitting. (10 agents, so far.)
This is what I "bought" for Laura Langie:
-- She has many other clients besides Meg Cabot.
-- For MG, she's not opposed to MS above 50k, or even 60k, and one 70k, which is good, since mine is on the high side of under 50k.
-- Reply rate is 81%, although I'm fully aware that is contingent on the queriers getting back to QT when they receive replies, so it's likely higher than that.
-- 32 positive responses in the last 12 months, with average response time 6 days, but slowest was 121 days.
-- 209 negative responses, usually taking less than a day to find out, but the slowest is 25 days.
-- 15 people, through QT, have been asked for partials or fulls in the last year.
The one thing I like about renting QT is I can see who her clients are to tailor my query to her. A good buy, since I'm not the Princess Diary type writer. (Nothing against Meg Cabot. I'm also not Hemingway or G. Neri. lol)