The inch of fish per gallon really goes out the window with planted tanks. If you're thinking about really slender fish, 12 sq in of surface area per inch works a bit better, and with planted tanks you could probably go even higher. My 10g is at well over 2 inches of fish per gallon, and just over 10 sq in of surface area per inch of fish, and everything runs like clockwork.
I'm pretty heavily planted with amazon swords, java ferns, java moss, anacharis, and random aponogeton bulbs that sprouted like monsters and are taking over my tank. I'm running a AQ20 HOB that's overpacked with biomedia (1.5 times the original amount) and stuffed with a huge chunk of filter floss.
I do water changes when I happen to have time for it, which is really only about ever other weekend. My nitrates go from less than 5 after a PWC to as high as 10 (oh no!) if i forget to do it for 2-3 weeks, and the fish have been perfectly content for several months now.
*edit*
it's definitely worth it to "overstock" your tank. I tried going with the inch per gallon rule, but quite frankly, it's a really boring tank. The 5 or 6 fish will hide in a school in a corner and never come out except to feed. With the way I've stocked, different fish are active at different times of day, and they roam all playing with each other. Each species has it's own hiding spots and favorite zones - danios on top, betta inside the plants, julli along the sides, emeralds under various pieces of driftwood and low-growing plants, and the neons just about anywhere they please - and they get along perfectly well, although I suspect I should never have put the danios in such a small tank. I cycled the tank with them using stability and prime a long time ago and they've stuck with me ever since.
