In a rather large (and growing) forum thread at the Apple Support Discussions, many designers have noticed that Snow Leopard is rendering fonts slightly differently, adding spacing where it shouldn't be, causing a major hassle for workflow consistency.
Poster "narc_monkey" reports:
Installed Snow Leopard on the first day, not a good idea. I am a graphic designer, I work in Quark and the Adobe Suite, with Suitcase Fusion 2. That said, not long (a couple hours) after I made the jump to Snow Leopard, I had work to do.
I open my first flash doc, activate Univers PostScript and I notice my whole layout has gone sour. This is because an extra bit of vertical padding is being added at the top of my text. It happens with some TrueType and OpenType fonts as well, while some others are not subject to the spacing issues. Very odd, and very menacing.
Just to reiterate, the problem is about 2.5pts (on 12 pt text) of padding on the top and bottom of random PostScript, OpenType, and even some TrueType fonts in Snow Leopard.
Several forum posters have submitted bug reports and stated that Apple is aware of this issue. Many power designers have reported downgrading to 10.5.8 to regain their normal workflow. Currently there is no fix for this issue from Apple, though hopefully we will see one in the forthcoming 10.6.2 update. For now, if you are a designer, be sure you have a stable backup of a 10.5.8 system should you encounter this issue.
Are you a designer that has seen this bug? Let us know in the comments!