I love kundalini yoga! I am actually studying to become a teacher. :)
Kundalini yoga does sound very spiritual on the surface, but it isn't a religion or anything. I am religious, so I dig it, but if that's not your bag I can see why it would put you off.
With the kundalini rising, it's not necessarily a physical sensation (though I have felt it a few times), but it's more of a change in your character. I have found, with a daily practice of yoga & meditation, that I am calmer, happier and more patient with daily life. I can cope with annoyances and difficulties that used to overwhelm me.
I've also used kundalini yoga and meditation to help me break my sugar & junk food addiction and lose weight. I've been very happy with the results. :)
I have heard stories about people having strange experiences once starting kundalini yoga, but here's my take on it. The meditations and kriyas are specifically designed to clear out the extra junk in the subconscious quickly. I experienced some crazy dreams and such when I first started, because all the negative emotions I had hidden away in my subconscious were brought to the surface to be cleared out. If you aren't expecting something like that to happen, you will be surprised and concerned, for sure. You might blame the kundalini yoga, but it's actually just a tool to help you to live a higher life, free of the issues that you've been carrying around for (possibly) years.
Kundalini yoga is also a specific science. If you don't follow the kriyas exactly (timing, posture, breathing, etc), you can end up with unwanted side-effects. A woman in my class accidentally skipped a page in her book while practicing at home, and ended up with a headache for the rest of the day. I skipped the last part of a kriya once and ended up with nausea for half an hour. Ugh! But I don't have any of those issues if I follow the instructions properly.
Feel free to ask any further questions. :)