Me personally, I never rotate tires. I have done the math, and, I would rather replace 2 very, VERY bad tires every year, than four worn tires that won't pass inspection anyway, every year. I put 20-25K a year on my cars... One to and from work, at 200 miles a week; and, the company car at 300+ miles a week.
Since PA requires state inspection, you fail for bad tires. Well, rotating them, wears all four, so you HAVE to buy four tires. Well, if I keep the front tires on the whole year, I only need to have those replaced when inspection comes around. So, I then move the rear ones up, and put the new ones on the back. Those now front will last a year, they just get worn down VERY low, till next year... That has been working for me for over 15 years, that's how I, well, ROLL...
4x4s probably require tire rotation to keep the ratios even... I got a 80k warranty with this 06 Lib, so we'll see how it looks when 12/09 rolls around...
I also try and buy tires that have the highest tread-wear number, 400+ if I can find them. I have been able to find 17" tires with 420 tread-wear when I had the Avenger.
Goodyear tires were the WORST, that's why they are called Good-Year, because that's all they last, with 240 and 280 tread-wear numbers...