Earlier today the US Apple Store was down with the usual message when it returned it didn’t look like much had changed but it appears Apple has added the option to upgrade your MacBook Pro to 2.16GHz.

The option is yet to appear on the UK Store.
[Update 1]
Apple have given a press statement regarding the upgrades.
The $2,499 model now includes a 2.0 GHz Intel Core Duo processor, up from the previously announced 1.83 GHz, and will begin shipping this week. The $1,999 model now includes a 1.83 GHz Intel Core Duo processor, up from the previously announced 1.67 GHz, and will begin shipping next week. In addition, customers may now upgrade to a 2.16 GHz Intel Core Duo processor as a build-to-order option on the Apple Online Store.