My take on this: If you watch 2001 on television (a crime in itself) then yes, the ape and stargate sequences are too long. But viewed in the cinema, 2001 isn't a frame too long. Indeed, I consider it the greatest science fiction film of all time. I also made sure my children's first time with it was in the cinema too (both loved it and were pleased I'd insisted we wait for rereleases - true love waits, and all that). :)