So, what did I learn about Porters that I didn't know before?
Well, I really like proper "English Porters." And, say what you will about New Glarus' Old English Porter, it undoubtedly fits into the mix with Samuel Smith's Taddy Porter and St. Peter's. There is a brightness to these British-style Porters, a lightness of palate, a tang, and a cleanness of finish to them.
Moreover, this British-style is almost exactly the opposite of the American-style, of which Great Lakes Edmund Fitzgerald is probably a classic and the O'So Nighttrain is a darn good runner-up. The American style is more full-bodied, if not truly a full mouthfeel, and a compound of roasted and coffee flavors and aroma. Any bitterness or bite comes from roasted malts and a more generous handful of hops. There can be some that are over the top, like Dark Horse's Black Bier with its huge chocolate and roasted malt profile, and some that are more reserved like Sand Creek's Badger Porter.
So, what are the dangers of the Porter? To my mind, the porter is an easy beer to make, but a difficult beer to make really well. The emphasis is on ease of drinking, but it can't sacrifice flavor - the porter is primarily a flavorful beer. To that end, many American porters can veer very, very close to being a stout; especially with the "heavying" of the stout. Finally, the emphasis here is on malts, though hops can make nice complimentary notes, particularly to help provide a clean finish.
To that end, much like the "Imperial Pilsner", an "Imperial Porter" doesn't really make a whole lot of sense. An "Imperial Porter" would be a stout, and mostly defeats the purpose of the porter - with its focus on easy-drinking working man roots.