I don't want to hijack the other thread about Brita, so I'm making my own.
I came across this the other day and thought it was pretty cool. It comes with a TDS meter too, if you're paranoid.
Now I ran the calculations on the replacement filters. If you got the pitcher (the one with a single filter) you should be able to filter 22.5 gallons before they recommend replacement (when TDS reaches 006). Filters can be bought in packs of 2, 4, or 8 for 30, 56, or 100 dollars respectively. With some highly advanced number crunching programs, I have determined the cost per gallon to be .67, .62, and .56 dollars respectively. Usually a gallon of store-bought distilled is 1 dollar (plus whatever time and gas it takes to get to the store).
Also, while they may want you to "replace at 006 for the product to continue functioning as advertised," I bet you can push it longer until it reaches 15 or 20 (I'd still use that on my plants). Have our prayers been answered? Is there really an affordable water filter than can give us acceptable TDS readings? I'm not sure. Maybe the company will go under in a year and you'll never be able to find filters again. But I think it's worth a shot. Perhaps I'll ask for one for my birthday.