It does show it's age in many ways, it lacks the gore of modern films (not a bad thing in my opinion) and it does feel a bit cheesey, although that's partly because it has been imitated so many times it lacks the rawness from its original release.
The film also feels a little clumsy in places, but it does do two things very well. The first is Michael Myers, you never really understand who or what he his and comes across as implacable and very sinister. The other thing is the music, the title tune in particular is very effective and works well with the film.
It might have aged a bit, but overall it remains an excellent watch and fully deserving of its classic status in film history.