There are two main benefits to running alloy rims:
As you mentioned, they are lighter. I read an article quite a few years back about sprung weight and un-sprung weight. Sprung weight is the weight which is above and supported by the springs. This would be like the body, engine, transmission, driver, etc. Un-sprung weight is the weight of the vehicle which includes everything below the springs, such as wheels, tires, brakes, etc. They said that 10lbs of un-sprung weight was worth 100lbs of sprung weight. If you can reduce the weight of your wheels/tires by 2.5lbs each, it's like taking a 100lb weight out of the trunk. This improves gas mileage, stopping distance, brake wear, and a plethora of other little things. These are very good things.
Aesthetics - Most people would consider that alloys look better than steel wheels covered by a hub-cap.
There is a down side to this, though:
- Cost - What is it going to cost you to replace perfectly good steel wheels for the alloys? A pretty penny, I'd suggest. The cost to get one fixed is going to be more expensive as well ... but how many times have you actually had to fix a rim in the first place? I've been driving vehicles for over 30 years and have only ran into the situation once, on one rim. I was young and dumb at the time, so never really got it fixed (let's just say lack of funds). The tire and suspension almost always takes the brunt of an impact. The only way you are going to run into the situation is by doing something dumb in the first place. Drive sanely and you'll probably never run into this situation.
You are going to have to decide for yourself what you want to do. If you have the funds and feel froggy, then by all means, jump on a new set. If, on the other hand, you are just responding to something "Dude" said, I'd say back to him, "Dude, I'll put some on there when you give me the money to do so!"