Okay guys (and girls-well someone mentioned them!)
MDF screws, if you must use that dreaded material(me included lately) then why not try MDF screws, and here is the link!!!!
http://www.quickscrew.com/screwmdfcskphillps.html .. and yes i have used these, pilot holes a must .. read later in this posting
now then HM, the cam and dowel fixing is designed specifically for use in chip board type substrates due to the deep thread upon the dowel section, and would delaminate the mdf very rapidly,
as for mdf fixings anyways, i once was given a fact sheet from one of my suppliers, which stated that any screw fixing must be countersunk, using pre drilled and piloted holes, due to the complete lack of compression available from the material...
hopefully this will help you guys(and girlies)
best regards 8) 8) 8)