I haven't purchased my monolight system yet, but the thing that I like about Alien Bees is their units come with an internal cooling fan, whereas most monolights in the same price range (JTL Versalight 300, Photogenic StudioMax III, Norman Allure DP320) do not.
The thing I DONT like about AB's is they look like toys...especially the brightly colored neon ones. If I didn't know anything about monolights, and I went to a photographer to have my portrait or event photographed and I saw neon pink and yellow lights...I'd wonder why he's using the same lights that illuminated the kick drums at the Poison concert. I know that's just my humble opinion...but I learned a long time ago that (unfortunately) perception is reality!! I want to be taken serious by my clientele.
However, its hard to beat their value (dollar for dollar), and since I cant afford Norman's ML series or Photogenic's PL series I'm considering a AB 3-light set-up with one B400 and two B800's (in black, of course).