Aquaguard may be a good brand, not necessarily all the products are good.
I was using Hindustan Lever Pure-It and happy without any problems, though had some limitations. service is prefect and you know exactly what your expenses are depending upon use and obviously no electricity charges. Then comes Auqaguard sales representative and he was good to convince us with the pros and cons of Aquaguard and Pure-It and finally I bought a latest product, Gold Nova, which was my mistake.
Always, always buy only a tried and tested product in the market. or you will become the victim to test their products at your cost. And when it comes to service, its 7 seven days now, I am still waiting for them. So before you choose your product, do a very good market research, especially regarding service.
Mind you, operation cost wise its never cheaper than Pure-it and you dont know what you next (regular) service cost will be, of course unless you take an AMC.