Flexi 7 has an option to smooth text (edit>prefereces>tools>text), but in Flexi 8 and up we now have an option to smooth everything (edit>preferences>general)
On most systems there is no performance hit, but we did find a few cases where you can see a big slow down. The option defaults to on in Flexi 8, and the special cases that have caused a slow down have been fixed in 8.5.