Jakob Nielsen's September Alertbox contains some pearls of wisdom, as usual

Nielsen's summary of the article says:

Users hate change, so it's usually best to stay with a familiar design and evolve it gradually. In the long run, however, incrementalism eventually destroys cohesiveness, calling for a new UI architecture.

He is absolutely right. Why Web designers are impelled to look for clever new ways of doing things, to confuse the site users, never ceases to amaze me.

Older web site users are really happy with the familiar. Unless your changes add tangible value to the user - don’t bother . Dick Stroud