The meaning differs depending on the context, as already explained in your another thread. When it means "well", it can be a softer version of いいえ、そうではありません "no, it's not", as same as in English. See the following example.
A : この言い方は正しいでしょうか?
B : そうですね、あまり正しいとは言えないかもしれないですね。
In this case, そうです can't be used instead of そうですね.