The Joule's plastic housing, impeller, and machining is as nice (or nicer) and easier to clean than my $799 Polyscience circulator. The heater is specially engineered and has a radically different design from everything else on the market. And it's waterproof. And smaller. And lighter. And magnetic. And it disassembles oh so nicely. And you can use it with almost no water. And it doesn't eat up the container with its giant profile. And it's quiet.
So long story short... no. I don't care that it has a synthetic housing. It's a quality synthetic housing. Metal wouldn't make it better, just different.