Seems to me that they're useful for very high handicappers just to get ball striking more consistent and finding a natural swing. Once you care about ball flight I can't see the usefulness.
In my opinion waste of money, You can only put those things so far ahead of you and it may appear you are hitting the ball straight and good well in fact you may not be. Being able to see your ball flight can tell you alot about what you need to do with your grip, stance, club face, etc...If you want to just work on your swing save yourself the money and just go swing the club outside and imagine you have a net there. Others may say different, but i think going to the driving range at $7-10 bucks a pop 4-5 times instead of spending 50-100 bucks on a net will teach you more about your swing and hitting ability than you could learn hitting into a net for a year.
Personally I like them...I know my swing pretty well and if I come through the ball square at impact I know pretty much what the ballflight is going to be...what comes and goes is setup alignment...nets are fine for working on keeping your setup consistent and spacing correct and practicing hitting the ball in the center of the clubface...it even takes away the ballflight so keeping your head down through impact rather than popping up to watch the flight becomes a non issue...good for working on mechanics and keeping things smooth...I vote a yes to nets...
I bought one just the other day both my wife and son have started golfing this past month and are having trouble getting a consistent swing and getting the ball off the ground. This seems to be helping them quite a bit. I personally dont like to use it.
I got one because it was on sale. Ten bucks at wal-mart. I've been working on just trying to hit the ball solid everytime. I think its only good for that.
I love my Net. I live up north where we can only play golf from April to November. I got the net set up in my garage and use it to get an early start on my swing usually in March. In fact I've gone through two of the nets in the last two years. That being said I dont use it during the golf season when I can get out to the range.
Pretty much everything said above is true. Ball flight is an important part of the the golf swing, and a net does indeed limit your ability to see the more subtle of errors. That is, you don't know if that was a relatively straight shot, a fade, or a slice because the ball doesn't have a chance to do anything in 10 to 20 feet.
But, if you get a monitor, like one of these -- Zelocity :: Golf Performance Monitors - Products -- they use doppler to measure what the ball flight would have been. They are pretty accurate, but expensive. The more money you put into it, the more variables the monitor can measure; for example, most of them measure backspin, but you have to spend a lot more money to get one that also measures sidespin. However, a serious player can get a fair amount of work done in a net with a monitor.
I love it and I vote a yes! I can spend 5 minutes or 5 hours and at anytime of the day or evening or late hours. It's great. I hit at at least 200 balls a day working on most of clubs (sw, 9, 5, 2h, 3w and driver) Yes, you don't see the ball flight but you can learn other things with it. If I see something on a magazine or on the golf channel about a technique or two, I'd run to my net and test them out right away. I can work on tempo, several short game technique ([pitching, chipping, chiputting, cocking wrist or not, etc). Usually I can tell if I'm pushing the ball or pulling it by just looking at where the ball hit the net. Eventually, you can tell or feel it if you hit a slice or a draw.
Just recently I bought a power meter that attaches to all your clubs and it has help me determine more or less how far I'm hitting it when I'm testing a new swing or a new technique. Of course, I still go to the golf range (or play a round) just to make sure and/or validate what I've been practicing is correct. If not I'll correct on the golf range, make a note and practice it at home - sure saved me a lot of money in the process as well.
I believe because of the facility at home to hit golf balls into a net help me improve from a beginner to an 80's player in less than 2 years. I say get it!