There are different times of "overtime". In IT, I'd recognize the following types:
- Certain work needs to be done outside of office hours. (Installing new memory in a server. Upgrading a database. Recabling the office, etc)
- Emergency. (Hardware failure. Software bug causing to lose business. Attack by evil outsiders. System overload.)
- Bad planning. (Deadlines)
I don't have a problem doing overwork for the first two cases; that I see as part of the job. The first one is usually planned. If the second one happens too often, something is wrong. The third one I'd be more reluctant. I'm not eager to do overtime if a salesperson makes promises to customers he isn't qualified to make; OTOH, I've worked for employers who do show their appreciation for anyone doing overtime (free food, parties during workhours after the deadline, give time off as compensation without any problems, not complaining if you cannot (or don't want to) do the overtime).
So, do overtime or not? It depends on the reason, the attitude of the employer, and the role you're playing inside the organisation.