blockbuster = block data right????
I just upgrade from 1Mb to 4Mb about 1 month ago. I asked the same question as you do now. So I think I should share my experience with whoever is interested to upgrade.
Overall, there is improvement.
Surfing: Not really noticeable much.
Youtube or other similar service: Improved (buffering time reduce quite a bit)
Download Rapidshare/Megaload (free service): Improved (from 50kb/s to around 90kb/s)
Torrent: I not really into it
Online gaming: Local - I do feel better. Oversea - I don't play
Stability: Improved (but stability can depend on many other things)
My happy index with internet connection: Improved

Sorry don't have much to share, I am now busy with setting up my new rig, so don't have much time to online.
do a speedtest... i subscribed 4mbps bcoz of direct download.... ntg else