If it were up to me, everyone would be training for their own personal function, swinging kettlebells, throwing around sandbags, and so forth. But let's face it-- if you're going to learn how to do these things right, it takes at least a little bit of time and money, and these are things that many people don't have right now. So a lot of people turn to Plan B: the workout DVD.
As far as I'm concerned, as long as you don't hurt yourself, if it's going to be a DVD or nothing at all, I'd rather you do the DVD. And if you're going to go that route, here's a few things you should keep in mind:
1) Just because they train celebrities doesn't mean they know anything about proper body mechanics. And just because someone lost a whole bunch of weight on their own also doesn't mean they should be training you. Case in point: Jillian Michaels (I say with gritted teeth). Jillian Michaels is big right now. Huge. She's everywhere. You see her on TV all the time, flashing her six-pack abs and screaming at obese people and making them run till they throw up (by the way-- don't do that). "She used to be fat," people often point out. "Look at her now!"
I do NOT recommend learning kettlebells from a DVD, or from someone who learned from a DVD. And I DEFINITELY do not recommend learning kettlebells from THIS DVD. If you're going to learn kettlebells, learn from someone who is certified to teach them. You can, and most likely will, injure yourself with bad form.
2) Remember that no one is going to be checking your form. So if you're going to be doing exercises on a DVD, you had better know how to do those exercises correctly, or risk injury.
3) One set of exercises done all the time is not going to produce results. If your DVD set doesn't have more than a few different routines, you're going to be disappointed. While (safe) movement is better than no movement, no matter what you're doing, progress will stop when your body gets used to your "routine." Get the word "routine" out of your exercise vocabulary.
4) You need to know your limits. If anything hurts in a bad way, stop. At the same time, you need to push yourself. If your muscles aren't burning, if you're not sweating mightily, if you're not progressing... something's wrong.
Honestly, your body is the best investment you can make. The combination of healthy foods and proper exercise are going to keep you healthier, happier, more energetic, more pleasant to be around, and will inspire the people around you (think: your kids, your parents, your friends...) to possibly live a healthier lifestyle, too. If you can manage it, get at least a few sessions from someone qualified to teach you how to work out efficiently and effectively to best benefit your lifestyle. And if you're going to do a DVD, make sure you do it right. I don't want to have to fix your back/shoulders/hips/brain after you tried "heroes" and "swing throughs."
Do your research. Take your body seriously. It's the only one you've got.