I haven't tried viper yet, but there's another version of emacs for OSX,
Aquamacs.  Has anyone tried to check slowness in Aquamacs?
...just a thought.
Cheers.
Fil

-- 
Filippo A. Salustri, Ph.D., P.Eng.
Mechanical and Industrial Engineering
Ryerson University
350 Victoria St, Toronto, ON
M5B 2K3, Canada
Tel: 416/979-5000 ext 7749
Fax: 416/979-5265
Email: salustri@ryerson.ca
http://deseng.ryerson.ca/~fil/