I have a Husqvarna Viking, but not an Opal, and I love it. I'm not sure if the Opal does this, but one of the things that I love is that the foot lifts up just a little when I pause, which saves me from constantly having to lift the foot for turns. I also really like the automatic foot-down feature (once I got used to it, which didn't take long). Both of those features allow me to keep both hands on what I'm working on, which sometimes really helps.
I can't speak for the Janome so I can't help you compare, but they're both good brands.