Now that I've been actually commuting on this bike, let me post an update, for people who might be interested in this either now or in the future.
I think the Linus mixte is a really nice bike. It is comfortable. The 8 speed hub works well and is convenient for me for switching gears, for example at a stop light at the bottom of a hill and before going up another hill. I've ridden it all over DC, including 13 mile rides from Georgetown to Silver Spring. On a side note, I've never seen another person actually riding a Linus mixte anywhere, especially not on the Capital Crescent Trail where I see mostly hybrids and road bikes. I've seen a few Linuses parked around in DC and seen one or two people on the Linus roadsters in downtown.
The bike has been a reliable vehicle that has taken me to the grocery store, to work and back, farmer's market, etc, and over gravel, mud, pavement, potholes, sticks, and even random broken glass I couldn't avoid, with no problems or complaints. I feel I can get on it and it will take me where I need to go. I can ride it for hours without discomfort besides normal backside pains from being a new rider.
It has reliably carried a pretty heavy, full bag of groceries or of commuting stuff on the back rack with no problems at all.
However--it is difficult for me to get up steep hills on my surprisingly hilly commute from downtown DC to Silver Spring. I can do it, but it's hard, and it's also hard on my hip and knee joints after a while because my leg muscles aren't really strong enough yet to push me and the bike up that 10th hill. The gearing also seems high.
I don't have much to compare it to but I think the bike is fairly slow. And something that I don't love about it is that it's a magnet for attention. It doesn't blend in at all. It's beautiful but that has a bad side when I don't want to talk to five different people every time I lock it up or draw looks from people as I pass in okay but not familiar-to-me neighborhoods. It sticks out like a beacon and I can't imagine compounding that by putting a Brooks saddle on it, not without people trying to steal the bike. Not a strike against the bike, but just something I've discovered that I never thought of.
Another thing I've discovered is that the mechanics at the chain of bike shops where I bought the bike don't seem to enjoy working on it or view it with much respect, which is a shame and is annoying. I guess this is because it's seen as a leisurely, fashion-y bike for poseurs, despite the fact that mine is a nice steel frame (not hi ten) bike that has been very dependable to ride. For people who want a "new vintage" style steel bike there are very few options, and this is one. I've felt that the mechanics haven't taken the bike seriously or me seriously, and that's been both a disappointment and a big push for me to learn to work on bikes myself to avoid depending on others. Again, not a reflection on the bike but still something to think about when purchasing one for commuting or anything else.
Because of the hills issue, I've decided to get a road bike and try that out too. I have a different post on bike forums about it. It's a 1987 Schwinn Voyageur that I got on CL. It is noticeably lighter than the Linus (which is understandable of course, bc it's a completely different kind of bike) and I want to see how riding it on the commute compares. I think I will end up alternating between both bikes for commuting. Once I'm in better shape I'll have an easier time with the Linus on hills.
Basically, what I've found is that the Linus is good for commuting, with a few caveats that could be dealbreakers depending on what a person wants out of a bike. It is dependable, fun, and resilient, but at the same time fairly heavy, can be difficult on steep hills, and draws attention to itself in an urban setting.
This has turned into more of a review of Linus in general but I thought I'd share.