We get very blurry text rendering when using HyperLinkButton. I think its most clearly seen when it has mouse on top. Also maybe issue becomes more transparent when TextWeight is set to bold for hyperlink.
I believe we dont have that many options in Silverlight to control text rendering, default TextHinting is Fixed, if we set it to Animated for HyperLinkButton it doesn’t really fix the issue, instead it seems to me that it creates a little different issue, but in the end text is still blurry.
So I am wondering how to get a good looking HyperLinkButton in Silverlight 4.0?
Strange that noone notices that, try to move mouse over control youll see it gets blurry/darker. Anything, but just underscored.

this is an interesting article about that very issue, which goes some way into solving the problem: http://peterbrady.net/News/Details/quick-fix-for-silverlight-hyperlinkbutton-rendering