I haven't seen any new issues with well designed PS fonts in 10.6. The last update to 10.6.7 had some problems with OpenType fonts, but that was just fixed with the previously mentioned patch.
Are the issues you're seeing with native PS fonts when used in 10.6 or are the issues with the fonts after they've been converted?
It's possible that you could have a corrupt font cache. Try clearing them out and see if it helps. FontNuke is a good free too for this.
jamapi.com :: FontNuke - A FREE tool for removing font cache files on Mac OS X
If the issues are after the conversion it's a prime example of some of the issues with converting a font from one format to another. It's not only legally wrong, but it often doesn't work that well.
Converting the Postscript version of a Font to TrueType (or other format) doesn't make the resulting font exactly the same as the native TrueType version of the font. Subtle differences in the underlying font data make the bastardized font wrong. It's like messing with the font DNA, and if the bastardized fonts get out in the wild, the unintended consequences COULD DESTROY US ALL.
Sorry, slipped into wild-haired rant mode for a second. Seriously though, I've seen a number of output issues caused by these bastard fonts over the years and feel like it's my duty to discourage their creation. Font management is already a big enough mess, and converted fonts tend to poison the well. They can be named exactly the same as the "real" version but won't output or are just different enough that they cause rewrap or kerning problems. Pay Adobe or whoever for a true OTF font or continue using the native PS font.
Anyway I'll put my tinfoil hat back on and go back to cleaning out corrupted screen font suitcases with my copy of Font/DA mover.
Good luck.
Shawn