well for sure my ranking did not improve even though i bough 3K directory submissions and 300 social bookmarks. Out of which I would say at least half of it were wasted, rejected, require reciprocal links, etc.
Quality submissions is still better than mass low quality ones esp now with Google new ranking.
I am now using a new submission service by a team based in Europe that owns a 400 US web2.0 property social bookmark sites. They gave me good quality links which saw my ranking improve, and saw many of my products going to top 5 position. They targetted 20 keywords for me on top of adding on long tail submissions on a daily basis. Anyhow, this is a separate matter but it works far better than the mass low quality submissions.