[compay]

On many sites, IE 6-8 users account for more than half of visits, and are often the single largest block of visitors by browser. Assuming you have such a site and don't want to just write off 50% of your users design-wise, it's nice to have the ability to use border-radius and other CSS3 advances, because they save you from a lot of time-consuming, repetitive work.

If you are in a situation where you can simply forget about what your site looks like in IE, then I envy you. Most web designers are not.

[smitjel]

No, that strictly depends on how you've designed your site. To have your site look the best in ALL browsers, make subtle use of CSS3 effects. Don't _rely_ on them. If you follow that, you won't be writing off "50%" of your users design-wise.

[compay]

Sure, but then you're writing off CSS3 and continuing to write code as if it were 2006, which I personally don't like having to do.