Have you considered Xcode?
I know you said you don't like TextMate, but it's one that meet pretty much all your needs.
which is fast
TextMate
Really fast
Xcode
Not that fast but not Eclipse/Netbeans-slow
which does syntax highlighting
TextMate
Very complete and extensible
Xcode
Does syntax highlighting, it depends on your needs
were I can define own syntaxes (or there are many plugins e.g. for YAML),
TextMate
Very, very extensible
Xcode
Syntax extensions are possible
where the developers are active,
TextMate
Some say it's vaporware, yet very few other text editor can compete with its current features
Xcode
Apple development of this program is very active
which does not have the look & feeling of TextWrangler
TextMate
If you don't like the sliding bar, there's a plugin to replace it by a drawer
Xcode
Doesn't have a sliding bar
which can define projects (like Coda can)
TextMate / Xcode
Do projects
which includes a basic support for Git and/or SVN
TextMate
Support for Git/SVN/Mercurial (and probaby more) via built-in and added plugins
Xcode
SVN support for 3.x, added Git in Xcode 4
which supports a fast autocompletion
TextMate
Basic variable/function completion
very complete code completion via bundles
Xcode
Basic variable/function completion
MacOS X 10.6 compatible
TextMate
Some compatibility issue
Xcode
Fully compatible
Best Answer
If Chrome isn't too heavy for you Google Docs has very capable spreadsheet facilities that improve all the time. You can even run it offline if you're going to be away from an internet connection.