You need to install it:
. because it protects you better than previous versions;
. because it protects others better than previous versions.
I do not want to share the internet with you if you do not stay current with antivirus, antitrojan, antispam, and antispyware releases from you OS vendor.
Your secure, and happy, use of the internet will surely become compromised at times in the current climate of malware everywhere. But you can fight the good fight, and should, both for your sanity and mine.
If SP2 poses an issue for you, ask here. I will remind you that:
. there are a lot of workarounds, and very clever folks here that can help;
. SP2-related support incidents at Microsoft are free of any charges: thread779-923312
Go for it.
Best,
Bill Castner