I personally think a thread per title/deal is better suited for readers. A stickied thread must be constantly monitored for deals, however a killer Steam deal in its own thread will probably stay near the top of the forum due to activity. Likewise, a crap deal will just sink to the bottom unless people are having off-topic conversations about it (hi).
I (and I assume many others) use the forum as a sort of filter to cut out the crap deals and the cream rises to the top - save for some flaming on "crap" deals. The stickies prevent the filter from running its course and we have to check each thread manually. I also think that the weekly ads are good for a sticky, however if there is a truly killer deal in those ads it can have its own thread. Everyone is going to have their own preference...