Gmail Mobile works really well on BlackBerry. Like Google asserts, it "Automatically optimizes the interface for the phone you're using". This statement is very much true since gmail preserves it's claim-for-fame conversation style on the mobile devices making it very easy to navigate and browse.
Check it out for yourself. Point your phone's web browser to http://m.gmail.com
Nauman further explains how to Search your PC/Mac from any Mobile device.