I'm just throwing this out there, but is there a way to make it such that other people congratulate you? people already do this on facebook (e.g., weddings, babies, graduations, new jobs, etc.), so you might have some adoption issues, but turning it around would alleviate the awkwardness of tooting your own horn. people could then post other stuff to it (like pictures related to the milestone), which they might be more apprehensive to do (or is awkward / cumbersome to link to a wall post) on a site like Facebook.

i think the reason it works on facebook (and personal blogs, i guess) is it's more fluid - people do actually post some of their milestones there ("Just graduated from X school!", "Just climbed Mt. Y"), and people comment on those posts, but it's a little different to do it on a site that's primary purpose is to pat one's self on her back.