The train's easy to use and very comfortable; whether you're using the French rail system or the German one. If Germany's going to be one of your routine destinations, and if you're going to use their outstanding Deutsche Bahn to get there, use thier website to look & book. I also recommend buying a DB Card. I have a DB 25 Card, which gives me 25% off any first/second class ticket I buy.

I love riding the trains in Europe. As long as you make it to the track you're supposed to be at before the train you plan to ride leaves, you're "on time"- so there's no bag-drag, no European airport security confiscating your chapstick, and no painful wandering around an airport because you got there & checked-in 2 hours prior. Good luck!