I have a disability pass because I have heart and lung problems and can't stand for prolongued times.
I must say that over time DLP has become a _lot_ stricter.
Some tips for people that need a disability pass:
If you do not have an official handicapped card from your country (trust me, I know what kind of bureaucratic drama it can be, over here in Belgium the procedure takes at least a year and half), make sure to get a note from your family doctor and/or specialist in French or English.
Preferably in French.
If that's not possible and you are an AP holder (in which case you need to sort it at the AP office and not city hall) make sure to go by city hall first, as they have people there that can either speak your language or find someone that can to translate it for confirmation.
That way if you are send to the AP office, you can at least say you already had it translated and ok'ed at city hall (which is what I did back in June 2009 because my GP note was in Dutch).
Don't lie about it though, because they will check.
I never had a disability pass refused because my GP note was in Dutch, but it's best not to take the risk.
If you're not obviously disabled then it can be a lot harder to get one so making it as easy as possible for the CMs is probably the way forward.
Also, if you are there with 4 people don't be afraid to ask for a pass that allows you to ride together with your full group. The CMs full well understand you don't want to get split up and are generally very kind and understanding in matters like these. I always found them friendly and nice at least, the lady who gove me mine last Saturday was even so kind as to laminate it for me ^^