Caught over at the Exchange Team blog, an article full of useful tips.
My new best friend is going to be the equals sign:
Putting an = in front of the e-mail alias that you are trying to resolve when composing a mail will automatically resolve it to any exact matches. Tired of typing johnr in to the To: line and being prompted as to whether you meant johnred or johnr or johnreb? Well no more, simply type in =johnr and the name will automatically resolve to johnr when you use the super nifty hotkey ctrl-k that you leaned about in hidden tip #1. This works in Outlook as well.
More at You Had Me At EHLO...