If you are careful, not worth the bother. It reduces the swipe sensitivity somewhat. If you can get one for under R50, then buy it. The screen must be spotless, no dust when you fit it
Yes they are worth it!!!!!!!! You will never hate yourself more than when there is an irritating small scratch in the middle of the screen!!! It's 10 times worse than a HUGE scratch. Get one!!!!!!!!!!!!!!!! Word of advice, let them put it on for you in store, else there will inevitably be a small speck of dust stuck somewhere.
I try to avoid the cheapies they tend to scratch or come loose after a week or so I tried the cheap to expensive one like the zagg it's a total pain to apply and the dust and lint started to build up around the edges making the phone look dirty.
My favourite ones I use now are Extrememac and SPG I would recommend you give those a try.
I have to agree, its a must for all your idevices. I have on my phone and my ipad. the phone i use the one that came with my otterbox cover and i have just put in the invishield onto my ipad and if you didnt know it was there you wouldn't see it.