I dont' think hotwire has bidding, but priceline does.
If I were thinking of pricline, I might check out hotwire, set up your trip on your account and "watch" it. Then check every day, being sure to click through what they first "offer". For instance, I've been following our trip for about a month now...sometimes it shows that the lowest rate is 32.95 for a compact (this is out of LAX), but I click "continue" and it tells me "good news, your rate has lowered". And it changes each day.
So i'd see what they are offering, and take that into account when making a bid on priceline (going lower than it of course).
I highly recommend betterbidding dot com for info. I studied that site before using hotwire for hotel and car...they also have priceline info. Absolutely invaluable information!