As far as I can see it's all powerboats, except for Bavarias. I'm not sure there's enough there to make it an interesting day out, unless you're in the market for something specific.
[Correction: Hmm, the MDL website says "Visitors will be able to step onboard Arcona Yachts, Axopar, Azimut, Bavaria Yachts, Bayliner, Beneteau Power, Beneteau Sail, Brig RIBS, Cobra, Comitti UK & Caribbean, Cranchi, Dazcat, Dehler, Discovery Shipyard, Dragonfly Trimarans, Dufour, Elan, Excess Catamarans, Fjord, Fountaine Pajot, Galeon Yachts, Greenline Yachts, Hanse, Hylas, J Boat, Jeanneau, Lagoon, Moody, Najad, Nautitech, Neel, Nimbus, RS Sail Boats, Sea Ray, Seaward, and Sessa" - more details here. Bit silly of the organisers not to update their exhibitors' list on the main website!]