Dietikon is a good place to get out. I did it 2 years ago, and if I remember correctly, Werdinsel - Dietikon was about 3 hours.
There is another Wehr at Dietikon, and looking on Google maps, there are 3 more before Baden, so I would not go further than Dietikon.
Another good one is Bremgarten-Mellingen-Windisch. Reuss is not as deep as Limmat, so the stones in the river makes it a little wilder. Dont jump in for a swim. The water is low enough, that you may hit the stones while swimming, and with the current, it can give a few blue spots. I do remember it as being better for swimming towards the end.
I have also done Andelfingen - Eglisau. Is great fun on the Thur, and also on the Rhine until ca. Rüdingen. then it just got slow. It was hard work to get to Eglisau from there, but great for Swimming.