The cool thing is that when slid shut, it's a solid (hopefully flat) top, but then gaps can be opened for mid-table clamping. I figure the top is 3 pieces of 12" x 30" x 3/8"(maybe be even 1/4" since it's pretty well supported with 2" angle around the edge.). When shut, the table is 30" x 36", but it can be opened to 5 feet, and even wider with longer bars.
The pluses I see with this are adjustability, mid-table clamping, and that its made of smaller pieces that I can handle without risking my back. The down sides are that I have to make lots of pieces for this and get the telescoping to work, and the risk that the results won't end up as flat as I'd like. I'm also on the fence about tacking or bolting the top on. With 12" x 30" top sections, I can fit them on my mill and put in some tapered holes.