Yeah, good points. Unfortunately right now I have almost no idea when I'll need the money because DH hasn't totally bought into MMM. He might decide to cut back his hours in a few years, or he might decide to work full-time for the next 15. If it's the former, then contributing to Roths is probably worse than pointless (although, and I forgot to mention this part, DH actually has a Roth already - not a whole lot, around $30K, and he hasn't contributed to it in years). But if the latter, he'll be a bit past 59.5 when he quits, so a Roth would be a ready source of cash.
I'll keep thinking about it. There are some interesting observations at sol's link about changes to tax law, too.