But it happens that I came upon an error when trying out the new image uploader and I'm sure many people will get it too:

PHP Fatal error: Call to undefined function ctype_digit() in wp-includes/link-template.php on line 182

What happens is that my flavor of PHP5 is not compiled with the ctype flag. This seems to be the default on Gentoo, so if you run it be sure to add the ctype use flag to your portage config. But if you can't recompile PHP, you can just open up the file wp-includes/link-template.php and replace the line 182 as follows:

Replace ctype_digit with is_numeric

That should do the trick until the version 2.5.1 that should patch things up according to what I see in the bug tracker (pending issue on link-template.php and a similar issue in another file already merged in 2.5).