Hm... it seems that it is possible to fly to Saarbrücken at a reasonable price; Expedia.de quotes a price of €97.97 (including €5 service fee, and with an optional €6 trip cancellation insurance, but apparently without charging postage for the tickets), and opodo.de gives €92.97 (plus €5 service fee... so it ends up the same, and plus €3 for postage and with the option of trip cancellation insurance for €15).
Kelkoo.de gives a flight for €99 at ebookers.de, which is also not much more. Hm, plus €10 service fee, and plus €5 for postage.
The flights are all the same: there on Friday 08:30–10:00 (which is pretty early; I suppose I could do a bit of sightseeing, though) and back on Sunday 17:30–19:00.
It's really the Sunday flight that is attractive: it would mean that I would neither have to leave at 12 nor get home after 10 or even 11 at night, since the train takes quite a long time.
I jokingly asked Stella whether she'd want to come with me, and she said yes (if she feels up to it and she thinks the kid would be fine; it'd be only about two and a half months old, after all).
Flying with her would give me something more "productive" and perhaps nicer to do on Friday: looking at the town together. And perhaps she'd pop into the qepHom occasionally and learn the odd word of Klingon :)
But the flight is operated with De Havilland Dash 8 planes, which are too small for her taste; she's wary of flying anyway.
So now I'm unsure what to do. She'd prefer that I wait until the baby is there before making travel arrangements, but cheap plane fares are notorious for disappearing if you wait too long. And the plane would be good for Sunday—though I'd probably have to take a taxi to the airport on Sunday, which'll add some money to the fare (public transport connections to the airport are abominable on Sundays).
OTOH, plane tickets at that price are non-refundable.
So it boils down to—do I think I want to make an eight-hour train ride (or six hours by ICE for more money) with a little baby each way? And come home fairly late on Sunday? And possibly get a variable amount of sleep due to having a little child in my room? (Though last time, my roommates tended to come back to the room at an ungodly hour as well, but at least they were fairly quiet about it.)
Or do I want to fly and probably not have Stella with me? Or something like that.
I think I'll be booking the flight soon. Probably from Expedia. Maybe.
Edit: Talked it over a bit more with Stella. Didn't come to a real conclusion.
The flight for three people (about €270 if the child sits on her lap) is comparable to a full-price ticket by ICE (about €300), which is 2–2.5 hours faster than the IC and which Stella would prefer for the trip. However, one can get train tickets for about €150 if you book far enough in advance.
On the other hand, if we took the train and made it into a little mini-holiday (perhaps returning on Monday rather than Sunday), we wouldn't have all that much time in Saarbrücken—we'd arrive about 16:40 on Friday and have to leave about 11:00 on Monday, so neither Fri or Mon would give us that much time together to explore the city, and on Sat and Sun I'd be busy speaking Klingon (or something like that).
So in the end she said that perhaps I should plan on going there by myself and making plans on the basis of that.
Which probably means I'll fly.
I suppose I could still stay an extra day, since public transport to the airport is much better on Monday than on Saturday (and getting to the airport should be quite a bit cheaper than taking a taxi), but I imagine an extra night at the hostel would cost on the order of the taxi fare, so I wouldn't be saving any money that way. (And I'd still have to pay for a bus to the airport.)