My mother in law has one on the main water pipe into her apartment, so all taps have filtered water (and the toilet flushes using filtered water I guess) The water taste a bit funny at times, but I've drunk it straight from the tap many times and have not had any laduzi attacks. 

There are different grades of purifiers, some will filter off more crap than others. To make a good choice you probably need to investigate what the problem with the water actually is. e.g. is it chemical or biological or both. Also, the filters will only be able to filter a certain amount per day, and will need replacing after a certain total amount of water has been run through them. 

If it will improve your health I can't say, but I am sure it will not make it worse. Compared to just boiling water, filtering is probably a good addition. 

We have chosen not to have a filter installed as we are renting the place. We actually had a guy come to give an offer on it, but he could not figure out how to just add one big filter where the water comes in, he wanted to add a small extra tap at each sink, so we stuck with having the big jugs of mineral water delivered, and tap water is only used for showering/dishwashing/toothbrushing. I do know some people who have the small extra tap next to the normal one, seems to work fine, albeit the water flow is a bit slow. It is probably where you get most for your money as the small filters cost less, requires less installation cost etc. 

1200 is a little expensive for a small reverse osmosis system.  I'm spending a little more than that for a 700gpd system I'm designing for washing clothes and taking a bath.   Small undersink system only produce about 50 gallons per day.  You can get them for about half the price you are paying.

If enough people are interested, maybe I'll post some pictures of the unusual installation. I'll be using a 70 gallon storage tank and secondary pipe routing to my bathroom water boiler.