If the system is there why not use it from time to time, Companies are happy to take the piss out of their workers so why not give a bit back.
Quite.
Companies these days want blood for their money. No harm in a few days bonus leave. Key things are
-dont have the worst sick record in the office
-dont stitch colleagues up so take sick day when full cover in
-build it up ie mope about the day before a sick day and remember to mope the day you return
-avoid being seen on said sick day
-If taking more than 1 day, update social networking sites with a status to reflect how ill you are , get a mate to back it up with a comment or 2
No harm in that at all