If you're using Dreamweaver mainly for HTML, I very much doubt that you'll notice any difference between MX and 8.
Again with the Flash, unless you are an advanced user there's little difference between Flash MX 2004 and Flash 8.
Also (and this is from memory) I think you get Freehand with Studio MX whereas they've removed it from Studio 8.
If in doubt, you can download the full version of Studio 8 from the Macromedia website and use it for 30 days with no restrictions. Speaking as someone who just bought Studio 8 for £650 + VAT (around $1330!), $299 seems a bargain, but I would say that it's $150 you don't need to spend...