Long story short: Black & Decker Parana blade cuts through MDF like butter.
A bit longer: I tried cutting through 2 foot of 3/4 inch thick Medium Density Fiberboard. It took about 20 minutes and produced a lot of smoke.
Whoa Whoa! Brian. Glad it worked out, but...
In future, Black and Decker nothing, ever. MDF wasn't prevalent when your saw was made, (neither were some fourm members). 20 minutes isn't a number within the most remote realm of consideration for a single pass with any power tool, unless it's like a 1700 foot pass, which would put it in tiny mountains somewhere.
The instant there's smoke, the incorrect something (tool, tool accessory, etc.) is being employed for the task at hand. (For all saw blades, consider correct tooth rake(s), correct # of teeth, and carbide. No Marathon, CMT, or bargain-priced Freud or DeWalt blades.) A good circ. saw with a good cond. blade can cut full 1" MDF (try lifting a 4 x 8 sheet of that) with no fight at all.
Every good quality 7 1/4" circ saw blade in a decent saw will easily cut MDF, even the wrong blades, like an 80 tooth veneered plywood/melamine blade. The only differences should be the quality of the final cut.
Home center MDF is crap. Go to a lumber yard with a chunk of the home center junk and compare. Look at how tighly packed the particles are in the good stuff. Also, it may come from China at the home centers. No home building material from China is worth your time and effort.
I haven't been burned, but I've had friends who had jobs go south because if it. If it's a (non-exotic, of course) wood product that didn't come from the US or Canada, just keep walkin.' Canadian was better for a long while. Now it's about even, since some Canadian wood products have declined in quality in the past 4 or 5 years.
MDF dust is highly toxic to inhale and will still be found on a dust mop weeks later, so be careful. I take absolutley no workplace precautions, because my death wish has been ignored for so long.