Yup, that's how I change my useragent quickly. As for Evernote you can use it without the app (you just won't get the offline notes when offline). I use it myself, though oddly the iPhone version of their website won't work with a useragent change (it shows up but it won't load the notes it just stays stuck on loading).

As for tabbed browsing, don't we have that already? Not through microb but one of the other alternatives? Firefox, or the browsers from KDE or Debian?

But yes, some of their applications are neat. I look forward to what Google Android has to offer in response (especially since we can install that on our tablets :P).