It's nice to see rounded corners being used in VB 4, but it's let down badly by the fact they don't work in IE (8 and maybe other browsers I haven't tested yet). I use malsup jquery corner on my sites. It's mind numbingly easy to use, very versatile, many styles, image-less (pure js) and is supported by all the major browsers.
If you are going to implement these sorts of features, which I think you should, they should be cross browser compatable or left out all together!
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