Like carwise said, it only makes sense for a modern small engine 1.6 or smaller, fuel efficent car if you really drive a lot. Ala taxi kung baga. But for big gas guzzlers like mine it does make sense. I get around 5km/l city driving and I need to use 95 octane so converting makes sense for me. If I use Korean system, I'll recoup my outlay in about 10,000 kms or 1 year driving. If I use the Euro system it will be a little over 2 years or 20,000+ kms.
Hopefully I can find a system that is in between the two. Newer technology but at a more reasonable price.