You're right about startup. But that can be mitigated with block heaters in cold climates, which are already widely used. Especially on little tiny engines. As well it's not nearly so hard to turn over a tiny engine, so I think the cold start problem is no worse than gasoline. A small engine will warm up fairly quickly.
I stood next to a big rig the other day when it was -40C (I was loading it), and it had no smell of diesel at all. Just a vague ammonia steam whiff occasionally. This is of course after it's warmed up. In my mind diesel is the only alternative in the future as it's the only engine capable of running without modifications on a myriad of biologically-derived oils. Heavier oil biofuels made by algae and waste digestion seem to be better bets than ethanol.