After wresting with a neighbors lugnuts on her F150 (ended up needing a 4 foot length of pipe on my breaker bar to loosen them) I decided to buy a decent cordless Impact. I was going to buy the Milwaukee 18v one but since I already have a number of DeWalt 20V tools I decided to get the DCF891 that came out earlier this year. It is currently on sale (last day!) at Canadian Tire with two 5ah batteries and charger for $439.99 (Reg $549.99). This one is rated at 800 ft/lb loosening power and 600 ft/lb tightening. It also has a "smart" setting that uses full torque to loosen but will slow to a stop once the nut is loosened and will also not overtighten a nut. This fellow did a review and actually was able to loosen a nut that was torqued to 900ft lb.
It was a big expense but also one I feel is a necessity given the amount of corrosion-siezed bolts I come across here. I'll be putting it to the test soon as my neighbor asked me to help do the rear brakes on the same F150 and I suspect the back wheel nuts will be as tight as the fronts!
I'm not sure Mark. I'll have to try one and see. You are correct about the improvements with cordless power. I have an Echo cordless chainsaw (58V) and love it. My son bought a pole saw (basically a chainsaw on the end of a long pole). It's 20v and I'm impressed how well it works (and how much easier it makes dealing with all our downed trees).
I'm adding a storage room to my garage these days and using my Dewalt stuff. Handiest tools I have even owned (other than maybe my dads old hammer) Tempted to buy one of the 20AH batteries I have seen on the shelves to avoid having to swap batteries just when its getting interesting (ie up on the ladder) but man they are pricey!