Just upgraded to the new version.
It's now slightly easier to switch the radios on/off (five clicks, including getting back to the text, rather than seven.)
The font changes are very subtle. I can't see any difference with my naked eye, but there are indeed some minor differences if you compare the screenshots. Both Futura and Palatino seems to have been completely re-hinted, but for Baskerville, the only difference appears to be a minor hint for the lower-case 's'
I attach screenshots with all the fonts using 5.2 and 5.3, taken with the smallest size.