Norton is of course both for Mac and Windows!
I use Win7 in network with another XP PC. Until i bought Norton Internet Security, I had some really dragging firewall problems between the two PC's. Until then I tested a lot of different antivirus programs. Either they screwed up my network or used to much processor power. All the time I neglected Norton, because I've had so much terrible experience with them in the past. That is, however, until i read some very promising tests/reviews + top awards on particularly Norton Internet Security 2010 and on.. (don't know about Nortons other products).
I decided therefor to give it a try. It turned out to be the best and most silent antivirus/firewall program that I've ever had!
Easy and intelligent firewall handling and low processor use - it even goes into sleep mode when in FSX. In fact you can manually configure which programs to implement the sleeping mode.
Believe it or not, but it is actually the first time in a year, that Norton seems to overreact on some, in this case, GSX exe files!
For that reason alone I obviously don't want to get rid of through Norton!
In the long term, however, one should always keep an eye to new development among all the antivirus developers - things change fast in that branch, so maybe ahead in 4-5 years or so Norton is crab again compared to others - but right now it is hot!