Keeping track of contacts

I have a system, based on a hacked GTD model that works quite well for me. It needs refining, and I'm holding off on spending too much time on that process, until I get the mac book purchased and learn new tools and applications.

One area that I seem to be the most disorganised in (and it stands out like a sore thumb), is contact management. I don't have a single "master" list of contact information, its spread about. Its not even spread about in similar formats, I've got an A5 filofax, Microsoft Outlook Contacts, GMail contacts, Locknote files and my mobile phone address book. Add to that the Lotus Notes address book of the company that I'm working at too.

Its not even that I know I have to look in the filofax for personal contacts, its really just every where!

So, when the mac arrives, I hope to consolidate all my contact information into a mac based application. The plan is to put all my contact information into Address Book.

What I need to know is - is this the best application to use? Does it allow contacts to have sensitive information protected? Thats what I use my locknote files for.

What do you use?