The answer to this question lies in what you intend to use your cameras and lenses for. Most people can escape without IS, VR, (or what other term your camera manufacturer uses to say that the camera and lens you are using minimizes the shaking of the person holding the camera) by using a tripod. If you are just using a point and shoot, chances are this doesn’t apply to you as most compact cameras now come with built in anti- shake devices.
If you often use a tripod, and nearly always have one near at hand, you won’t really need additional vibration reduction. That is what tripods are for.
If you have to shoot at low shutter speeds, but are in a situation where a tripod or monopod is impractical, and being able to shoot at one or two stops faster, a built in stabilizing system can start to become practical. At this point you have to begin to consider whether shooting two full stops faster is worth the money.
Some SLR cameras have the vibration reduction built in, meaning you don’t need a whole series of pricey lenses. I have heard mixed reviews on these cameras, some people loving them, others… not so much. This type of camera could save you a lot of money in the long run- if the rest of the camera works to your liking.
Built in vibration reduction greatly increases the cost of the lens, and sometimes of the camera itself. It can easily add a few hundred dollars onto the price tag. For me and my style of photography- kayaking (where tripods and monopods are counter productive) two being able to shoot at ISO 800 instead of 1600 makes a huge difference. I have images of bobcats that I captured crisply in low light, because I have image stabilized lenses. Most of the time though it is extraneous.
Every tool has its purpose, and these pricier lenses can be indispensable for some, but not all of us. Buy one if it is something you really need, not just because they are cool tech.