the short answer is "a LOT".
Now you may be asking two questions here;
a) how to make a set of css to make a browse look just like that (ignoring functionality). This is possible, and not terribly hard. Watch the webinars on Css, and start experimenting. Note that you can "see" the settings used by one app just as easily as you can set yours, so it's pretty straight-forward.
b) If you're asking if the NetTalk template could use the Flex Grid control as the native browse control, then the answer is no. jQuery are working on a Grid control, which will be released with jQuery UI 2.0, and it's _possible_ we'll incorporate that in some way - but the native NetTalk control has a huge amount of functionality and there are gonna be things it does that any other grid doesn't do, and trying to smoosh stuff together doesn't work really well.
Cheers
Bruce