I just recently purchased a Compactenna Scan III, and so far it seems to be doing the trick. I use it as a stealth antenna at home, however it's mainly used mobile. One thing to consider is that it uses a NMO mount, and has a rubber washer that it screws down onto in order to keep it waterproof. So, you'll want to be real careful if you go through the car wash with it, as high pressure water could infiltrate past that washer if it gets hit directly. Otherwise, from what I've read of other people's experience, it's weatherproof. Also, the center contact on this type of mount can get kind of loose if you're always removing the antenna from the mount (something that is not recommended). That being said, you can always pull that springy contact on the mount back up to its original position, so no real harm is done. In addition it's housing is basically a plastic cylinder, so I cannot comment on its durability over the long haul, but it appears sturdy enough to me. It's only about 9" tall, so the chances of smacking it into something appears very low. As long as you're not whacking it into things all the time, it should hold up. It's also a bit spendy at around $120, so perhaps a whip may be more economical, and more than adequate for your use. As the man said in a previous posting, you might do well to nail down what you're interested in listening to, and then buy the antenna appropriate for those freqs.
In the end, I got it because it's pretty much wide band, for the most part, and it works really well usinq a mag mount on my air conditioner housing. I'm kind of impressed with it, but then again I might be one who is easily impressed! I don't have specific details at hand as to the exact freq. bands, but HRO or DXE should have more than enough info for you to decide. People using it, myself included, find that it picks up pretty near everything you might be interested in hearing. I'm happy with it but, as always, YMMV. Good luck, and have fun!