there are many owners of the shark who post on the vectric forums as the vcarvepro software is included with it. i have several friends who have upgraded to larger machines and still keep the shark. there are som new table tops on the market as well
look for the hardware forum near the bottom
camaster has the stinger www.camaster.com and www.camheads.org
shopbot has the tyro which i have yet seen to be in the hands of an end user.
blurrycustoms has a table top as well, looks like it has some real potential just have yet to see a lot of them on the forums.
i have the camaster cost about twice as much as the shark but is built with industrial components.