Well, this is the kind of tool I've been waiting for. I've already got it as a homepage and managed to import all the important anneversaries and birthdays from outlook. As all things Google it is beta (gmail is still beta!)
It took a little bit of scrubbing. 1st I had to export to csv, then I scrubbed the data and cleaned out all of the rubbish entries & useless reminders until I was left a simple list of the dates I wanted. I then imported to gcal. The problem therefafter was checking them in a list view and individually putting in the annual repetitions in the reminders.
All in all not too bad a process and I'm very glad I've done it. Now I won't miss any of those important dates and keep track and update from work, home and anywhere else for that matter.