Those 5 gallon jugs of RO are good. I used them for quite a while when I first started. Make sure you check the params for nitrates and phosphates. I used to get mine from Save-on Foods where they have there own RO system. I used to have to tell them to change their membranes
When I moved closer to work (7 min drive) I started using the Millipore system we have in the lab (makes RO look like swamp water... It's excessive but if ya have it, use it!). However, the inconvenience of having to drive there, fill up the jugs (which takes a while), drive back, and lug them up three flights of stairs has me looking to purchase my own RO/DI. The amount I'd save on gas would pay for the system.
Now, the retarded thing is... I develop desalination technology for a living. Why the hell have I not built a prototype to use at home?