Rendering of web fonts on Windows XP is one big issue that there are solutions for but it really takes a lot of tweaking. First, it starts with a well designed and created font. Second, hinting can be applied that helps shift around the pixels on the screen to better map the outlines to the pixels on the screen, ClearType does help in some instances but mostly with small text, using tricks like sending WOFF/CFF to turn on GDI grayscale anti-aliasing is another that is employed when a font is a certain size - usually larger sizes.
Its one big issue and one that all of us web font service providers are trying to help solve. If we all had the resources we would be sending down one specific version for each browser / OS and screen setting combination. But that is pretty prohibitive. We are starting to see better renders built into the browsers and some tweaks that the folks at Webkit, Mozilla and IE are making.
The fact you are waiting 30 seconds is agreeably a poor experience but this should not be the case. Font files on the web range in size from 20kb to 120kb depending on the details in the font - I consider this file size to be nothing more to wait for than say a normal image size. Technically fonts can save on total downloads if you think about the number of images that can be replaced. Fonts from services like WebINK, Typekit, Fontdeck, Fonts.com are all served from global CDN's that have these files located regional servers that should be bring the fonts down to your browser in 500ms to 2 seconds at the most. Of course connection speed matters.
Chrome/Webkit will start to support the OpenType features version 18 from what I have seen - no idea about Safari yet. The current Canary build has support built into it but at this time it is only for Windows and not on the Mac. Not sure about the issues around the Mac and why they might not support it out of the gate but I assume they are working on it.
They will use the -webkit- prefix for the font-feature-settings. So like most new things we will have -webkit -ms and -moz until it settles down.
Its one big issue and one that all of us web font service providers are trying to help solve. If we all had the resources we would be sending down one specific version for each browser / OS and screen setting combination. But that is pretty prohibitive. We are starting to see better renders built into the browsers and some tweaks that the folks at Webkit, Mozilla and IE are making.