We tried two different rooms because we extended our booking.
Both rooms were spotless and quiet. Everything was modern and in good repair. If you want Old World charm, this is the wrong hotel for you, because it looks like it was remodeled yesterday by a perfectionist.
The smaller room was...small. Not a shoebox, but on the tight side. The larger room was considerably more comfortable, and it had a tub. If you're staying in Lucerne for more than a couple of days, I would recommend going for a bigger room. Either way, it won't be cheap, so you might as well enjoy yourself.
The curtains were really something. When we woke up, we couldn't tell whether it was day or night.
The staff was extremely professional. No issues at all. They could not have been better.
I didn't see any sign of a gym. If there is one, they hid it pretty well.
Walking to the river and sights is not difficult. I recommend it over buses and cabs.
Personally, I would try to find an older hotel in a more interesting neighborhood next time, but that's just me. Your stay at the Cascada will be trouble-free.