erm...it already uses Microsoft Sans Serif everywhere...
Except the stats screen where it switches to a monospace one for alignment reasons. For the scan results tree you can specify a font yourself (e.g. if the default one does not support all the utf8 characters which your currently loaded database require)
But yes of course..why not switch to something more modern...sure...if I don't have a job, a wife and 2 boys which steal 99% of my free time ;-)
Regarding the button bar....we're now living in a world of flat apps tiles..so maybe I change it to an UTF8 character plus and underline caption...hmm..nah...we'll see