quincy:
I have two Falcon "frames" (for lack of a better term), one old American and one later English, plus a variety of briar bowls for them. Because the frames are fabricated from aluminum they are lightweight and disperse heat well. The frames are also durable.
My Falcons smoke well, and I recommend them. Rather than using their Dry Rings at the base of the bowl, I simply used clipped pieces of pipe-cleaner formed into an appropriately sized circle. This helps to prevent gurgle with blends which tend to smoke wet.
Falcon was the original brand of this style of pipe, but a number of competing brands subsequently appeared. I have not tried any of them, and so cannot comment on their smokability or lack thereof.
Regarding the interchangeable frames and bowls, Richard Carleton Hacker once calculated that (at the time of the publication of his book titled "The Ultimate Pipe Book") there were 13,680 possible combinations!