We wrote this site in 100% OO PHP4. We now have 5 webservers, 1 sql server, and 1 nfs/web server. Our old setup (using php nuke!) required 2 web servers, 2 sql servers, and 1 nfs/web servers.
Not exactly necessarily a fair comparison, eh?

- those 5 webservers could have P75s while the 2 webservers could have P2500's
- the new 100% OO PHP site may have tons of more features since the phpnuke site
- the coders might have been lousy compared to PHPNuke's coders (I know, theoretically...)

So you see, such a statement does not say anything about OO. Also, the fact that OO performs slow does not mean "OO sucks" it means that the language in which OO is written (in this case PHP) has a flaud OO implementation.