I've test converted some solutions from v6.4 to 8.5. Once in v8.5 the screens look horrendous because of what the conversion did to the fonts.

Is this problem likely to be fixed in a version update or do I have to manually fix all 60 screens in my solution to make them look nice again?

This article should explain things:

http://filemaker.custhelp.com/cgi-bin/filemaker.cfg/php/enduser/std_adp.php?p_faqid=564&p_created=1115172450&p_sid=aYCBx7ji&p_accessibility=0&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9NTMmcF9wcm9kcz0wJnBfY2F0cz0mcF9wdj0mcF9jdj0mcF9zZWFyY2hfdHlwZT1hbnN3ZXJzLnNlYXJjaF9ubCZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PWZvbnQgNw**&p_li=&p_topview=1

And... no, there is unlikely to be a change to the way fonts anti-alias.