Rounded corners have always bugged me because they're always, always aliased in some way. The 'line' just isn't optically smooth, it's approximated. I personally prefer a clean corner to an approximated curve.

Similarly, in the first example, while I like the transparency effect (probably not for a map), I hate the current trend to have everything 'shine' when it shouldn't. Much as I'm not particularly keen on Win 8, I do like their idea of being 'authentically digital'. In the first example, I'd much prefer to use the UI on the right - even the text looks clearer (it's just not "whoah, cool, printed in glass!")