The problem with email is this: for many it's old and inefficient, but everyone's so used to it that it's hard to change their daily email reading habits. At the end of the day, all the extra features that services such as Zenbe or one of its many competitors - Fuser, Orgoo, Jubii - may offer, can simply confuse you and make you go back to the way you read email before, without "connecting to your friends" or "sharing your emails with everyone you know."
Zenbe, however, has gone so far integrating everything into its service that it's no longer an email aggregator; in fact, email - although still being the central part of Zenbe - is just a tiny part of what Zenbe can do. The service can perhaps best be called a social networking hub, giving you access to various webmail services (Gmail, Yahoo, Hotmail, AOL), social networks (Twitter, Facebook), chat (GTalk) and several other features (calendar, task list). Other features include ZenPages (which enable you to share stuff with your friends), mobile accessibility, and previewing files from all of your emails in a single pane.
All of this is set inside a neat, tabbed interface that I could definitely get used to. It doesn't all work perfectly, though. I haven't been able to connect with my Facebook account from Zenbe, and Twitter also had some problems: Zenbe insisted that it was down while it was, in fact, chirping happily in Twitterland.
Minor bugs aside, Zenbe fares well compared to the competition; the real question is how good it'll be at making people switch from their Gmail and Facebook and start using Zenbe on a regular basis. It's hard to tell, but it's a solid service which deserves to be given a try.