Years ago, long before Plaxo tried to become an aggregator, I became a member of Plaxo. I liked the online address book and calender that could easily be synchronized between different services. It quickly became the hub between my business Exchange infrastructure and private Mac/Google infrastructure. It all worked flawlessly and I'm sad about the changes.
Soon I need to start paying, a good moment to evaluate the value of the service. I've realized that over time the value of a synchronized address book and calender has become less and less. My iPhone now natively supports my business Exchange and the only thing left is the availability of my calender on my Mac. However since a while now Mac OS-X synchronizes the address book with Google and soon with the release of Snow Leopard also Exchange will be natively supported. This significantly reduces the need to synchronize calenders and address book.
I haven't yet evaluated any alternatives in detail, but I do know that the Plaxo value is NOT worth EUR 42.95 per year. I most likely will cancel my Plaxo membership, because the original reason for joining will be removed. All new features added since I joined haven't excited me at all. FriendFeed is a much better aggregator and LinkedIn is a better way to manage my business network.
Plaxo, I'm sorry... You have disappointed me!