The FontLab application is very light (only a few megs) and its vector engine (when resizing characters) is very fast even on my old 2x533 Celerons machine. Among its features you will find that there is a Glyph editor, support for a number of font formats (TTF, Type1, OpenType CFF, PFB, PFA and its own format VFB). The applications supports TrueType & Type 1 hinting which allows for better looking fonts on smaller sizes, while another useful feature is FontAudit (checks character outline while you edit it). The app also supports plugins and transformations, metrics and kerning editor with automatic functions and full support for Multiple Master fonts, full support for Unicode encodings with multiple codepages and optional font reencoding. Double-byte Codepages for Chinese, Japanese and Korean fonts while you can create Arabic and Hebrew Fonts - right-to-left writing is supported in all panels and in the Metrics editor. There is also a Python script interpreter inside FontLab lets you extend FontLab features by making your own tools and plugins.
As you can see this is the one application for font creation for your OS. It even allows you to load, edit and export existing fonts, so if you do not feel all creative, you can "hack" around existing fonts and then save them with another information and name (not that this is legal of course, but FontLab let's you do it... ;-)
I used FontLab for a few days last month, and my only problems would be the rather loaded UI which is difficult to understand as there is no help included with the application! Users would have to use the 700-page printed manual when they buy the full box or download a PDF file from their site (problem is that the PDF does not have good search features as in the standard "Help")...
The second problem was that fonts created with FontLab on really small sizes (7 and 8) were not exactly as good as advertised, or as good as other well known fonts like Arial and Verdana (even the sample fonts coming with FontLab, like FreeSans and FreeSerif were not as good on small sizes). People might need to mess with the TTF "programming" language in order to get the best quality out of their fonts on small sizes.
The only other professional font creation tool is of course Fontographer from Macromedia, but unfortunately this application has not been updated for years, plus it is featureless compared to FontLab.
FontLab offers its application for MacOS/OSX & Windows, it sells for $549 USD and I believe that it worths every penny. It is a full featured application and obviously a real pain to develop (as in "complex"). Operating system makers are encouraged to at least download the demo and try it out if they are serious about creating unique, high-quality fonts for their OSes instead of paying thousands of dollars on licensing ready-made high quality fonts for use with their OS.