Many say that keeping your body guessing is a good idea. That is, a variety of exercise modes, and keeping away from the same pattern of exercise time after time. May or may not be true, but there's no harm in changing things up, elliptical one time, biking another.

I don't know if you mean every day, but I've been convinced that strength training more than once per week is not worth the extra effort. If you enjoy it, or are out for maximum bodybuilding results, go for it, but I switched to once per week a few years ago, and am very happy with the results.