I'll grant to you that there are other products out there that are better than McAfee and Norton,BUT,
and this is a big
but (as is my butt )
in the business world when you are selling your services to medium and large corporations (and many small companies too), they don't want you to walk in with a laptop running 10 virtual machines, with 5 operating systems, and every tweak known to man. They want safe and stable - and preferrably configured just like what they use or really close to it. This means you should only have the generally accepted applications and developement tools that being used by the businesses you market your services to: Win 2000 Pro/XP Pro, McAfee/Norton, IE, SQL Server/Oracle, MS Office Pro, Outlook, Visual Studio Pro (if you're doing .net), FrontPage/Dreamweaver, and a few others.
If you don't use the software you clients/customers use, or know how to use them then you will lose business and they will hire someone else.
If you're going to work with businesses that use Linux, then by all means use dual-boot and create a Linux partition. But the same rules applies. Your Linux partition should only have the generally accepted applications and developement tools that being used by the businesses you market your services to.