As Michael Kimsal points out, there's a new posting on his brother Mark's blog talking about alternatives to addslashes() in your applications.

I've seen a lot of people talking about mysql_real_escape_string() vs addslashes() vs addcslashes(). There seems to be a lot of real confusion about what these functions do (even with the php.net manual around), especially when it comes to character sets. [...] So, I've decided to lay it all out in a few charts so there is no confusion about what each function does and how each can help protect against SQL injection attacks.

He ran some tests based on what the function does to see if it helps with certain things like "escapes with single quotes instead of backslash" and "prevents multi-byte attacks". He compares the speed and testability of the functions as well as provides a multi-byte breakdown oh how the mysql_real_escape_string function works with different character sets.