Thanks everyone for all the suggestions! I ended up ordering a Marathon Plus for the primary commuter, and a regular Marathon for the rear wheel of my new Motobecane Fantom CXX (the CXX will get used on dirt paths occasionally in addition to road riding, and Schwalbe rates the Marathon slightly higher than the Marathon Plus for off road).

I'm now intrigued with the Vittoria Randonneur Pro as a lighter, faster rolling road-only tire that is still very flat resistant. I'm going to keep that in mind if I find that the Marathon Plus feels too heavy/sluggish.

Thanks again!