The capability to address known and anonymous leads is really powerful, all the more so as that you can sync any field you want from the database for known leads and use them to create WP Target segments. Te ability to combine known and anonymous visitors are quite unique on the market.
There quite a few limitations, still, IMHO. Some of them (See possibility to use the same attribute twice or more in web personalization segments ) are really frustrating because they lead you to create simplistic segments. For instance, it's impossible to target anonymous who has visited at least 2 pages out of a list of 4. Or know leads who are either a customer or a small company.