Implementing SSL site-wide means encrypting every element and requiring authentication for all requests.
This is absolutely ruinous for performance as it increases the processing load on the server and typically trebles the
number of requests required to download data.
The Net panel in the Firebug extension for Firefox, or Fiddler will show where SSL is being used.
A pair of 401 return codes before the final 200 success code for more than the initial request indicates that secure connections have not been made persistent.
It is also worth checking the size of the 401 error page returned as this is another potential source of delay.
Only secure what you have to - don't assume SSL is an appropriate default.
When to use SSL
Check any 401 errors.
Troubleshooting 401 errors