I think I'll try it with escape() and unescape() for all browsers. Should still get some good compression savings, but it will make the code more manageable. Today it's IE that doesn't work, tomorrow it's something else. This compression is already way more savings than the plain data so it's a win/win I think.
The one thing I hate about web programming are these browser specific things. Drives me nuts (can you tell I'm new to this