I didn't think the film was slow.
The best bit for me is all the way up until the stupid holographic briefing and that's the slowest bit of the film.
I've seen it three times now (twice more than it took for me to fall in love with Blade Runner)
Naturally I will see it again.
If I can stoop so low as to buy the truly hateful AVP:Requiem, for completion sake, it would be narrow minded of me to not get Prometheus (the deleted material and the collected viral videos are worth the price of a second hand copy alone).