We've all been there, with 56K's.
Lifted directly from Spybot's description of marketscore "Marketscore monitors your surfing, essentially logging information about the webpages that you visit and the actions that you take, such as the purchases and transactions that make..... Please note that while we do not sell any personally identifiable member information, we do share personally identifiable with those third parties who help us deliver the marketscore service to you"
IMHO, its not worth it. Differences on 56k are hardly detectable and it'll do nothing for a broadband connection. I'd recommend using spybot to get rid of it and clean out the registry entries because the majority of uninstall options on software like it are very poor and leave too many bits behind.
If you're looking to tweak a broadband connection try
this tweaktester on DSL reports. It doesn't install software on your machine, just helps you adjust the (highly esoteric) settings. Don't ask me what those settings do though, I haven't a clue.
hope this helps.