When I first installed this, I was asked if I wouldn't mind sending back 'anonymous' data, to help improve the product. I declined, as I always do.
It's isn't overly intrusive, has a well-deserved reputation and has good reviews from Cnet.
However, Trend Titanium
is slightly better when it comes to the not being intrusive. (Their 'cloud updates' just make it so easy). Norton 360 v5.0
is also comparable, so I would maybe do a search and see which is the cheapest, at the time of purchase. (Other versions of Norton packages I've used have been resource-hogs, so make sure you check its 360 version)
Kaspersky Pure only seems to check Internet Explorer for vulnerabilities. I hate Explorer, I'm surprised people still use it, to be honest. It's good practice to always check for updates to Adobe Flash, and Firefox, for example. (What happens is - security 'holes' are found, the developers 'patch' those holes to stop bad people doing stuff... but people don't always stay on top of this)
== Do you really need to pay, at all? ==
If you're particularly skint, perhaps you can settle for a free package, like AVG or the one from Microsoft.
Don't let _any_ security package lull you into a false sense of security. Be really careful about the websites you visit, use the Web of Trust plugin (it's a free, community driven project, where people flag up dodgy sites)