Yep, we also noticed that the web page loading is a kind of slow ;-) We also tested other PHP-based CMS systems (like Typo3, CMS Made Simple) on the same hosting environement and they look like they would perform faster than SilverStripe.
Probably it is due our hoster is using php as (Fast-) CGI module. But this is very common because only in this configuration you are able to protect files of other users in a web hosting environement.
Well , with Sapphire being quite a powerful and complex framework , Silverstripe is performing a bit less than the alternative more simple solutions systems out there. This being said, I can't say that on our host , the performance is below par , or annoying.
Only thing I can think of is using either an optimizer or a cacher .... If you really need raw performance , you might want to try out the Silverstripe static exporter (search the wiki for it) ......