I've seen this second season of Strike Witches (all 12 episodes). It's pretty good, cool new weapons, new enemies, etc. Best new attack is Reppuzan, an energy shockwave sword attack performed by Mio Sakamoto using her newly forged magical katana (said sword is named Reppumaru).
However there's a downside. It has even more "fan service" than the first season. While you might like this if you are into ecchi, it will probably be a turnoff for most ordinary fans of scifi/fantasy anime including probably some of those who watched the first season of Strike Witches.
However if you can force your mind to ignore the scenes involving indecent humor, you will probably be able to get through watching this with your brain still in tact. If you are a scifi/fantasy fan, it will probably be worth it to watch this anime. Just remember that if you aren't also a fan of ecchi, you should probably close your eyes during some scenes.
Using movie MPAA ratings, this would get an obvious high level R, or possibly a low level NC-17. Using TV ratings (due to that it is a TV series) it will be TV-MA (which is what I hear it will be rated when the Bluray disk is released in the US later this year). So you should be at least 17 before watching this, and possibly waiting till at least 18 would be good advice.
Here's a video of Yoshika doing her ultimate move, True Reppuzan, using Mio's sword.