Setting up a website isn't the problem. There is adobe GoLive and Macromedia Dreamweaver for that. The problems come in when using Javascript. Safari just aggrevates me everytime I use it! I think Steve has Gatesitis! Like Bill, they have their own quirkyness that is just a horror to debug. The Console is basically worthless. Looks like I have to upgrade to OSX 10.4 to get proper tools, but thats because I am programming highly interactive sites. For normal sites with maybe a forum or ecommerce, there should be no issues for you. The problem is that these other sites set up THEIR websites to be windows-centric, but that doesn't mean YOU have to.
So I would say you should be just fine. Firefox for the Mac is excellent!