I have a few things to comment on...
First of all, I also ran Spy Sweeper every night (well morning around 5AM) .. and every morning when i woke up I had around 3-5 things found on my computer. This was a consistent trend for close to 2 or 3 months. A few weeks ago, I installed firefox. After a week of surfing the same website, and running the scan every night... I made it over a week without 1 object found. Since then, nothing has ever been found.
Note: I have, and always have, updated my software (especially IE) to always have the most recent updates as soon as they come out. I would consider myself an educated 'web surfer dude' so I generally have a clean computer and avoid the pitfalls your typical user would fall into. But, in spite of all this, i still got spyware junk.
Moral of the story is, TRY
Firefox out for a week and decide for youself. Join the 23+ million people who have made the switch since November 9th. (Source: www.spreadfirefox.com)