@heavanet- I have used a tension shower curtain rod, and you are correct about this type of rod being simple to install. It is very nice to buy one and put it into place with your shower curtain on it. Just like that, you have a shower curtain rod and curtain in place that are ready to use.
However, as it often is with anything that is so simple to use, there are some potential problems than can occur with this type of curtain rod. The most obvious issue is that a curtain rod that operates with tension can just as easily fall down. When I used a tension shower curtain rod, it often fell if I tried to use a shower curtain that was too heavy, or would put clothing or towels over it.
Another problem with a tension shower curtain rod is that you can't use it on certain types of wall surfaces. For example, this type of rod works best on a porcelain or fiberglass shower stall walls. On the other hand, if your shower walls are made of drywall, a rod that is held up by tension can easily punch a hole in the wall. This happened to me several times when I used a tension shower curtain rod.