I find it funny that this topic is brought up.
I've been wondering about that switch myself.
Lately, I've been driving it in Power mode. I find that the shifts are a little better for me because it runs the gear a little longer. I also find that it will down shift with a little less throttle than normal, which works for my application better.
I guess with it in Normal, it shifts normal and drives normal, but for my lift and gearing I found that it shifted too soon and I felt like it was lugging or underpowered.
I was even thinking of selling my Tracker because I didn't like how sluggish it was. Then, I flipped the switch and paid attention to my driving, speeds, roads, and down shifting.
Now, it is NOT a Night and Day difference, you will have to pay attention to it and think of those examples when comparing differences.
Also, I have the O/D turned off 95% of my driving. I stay in town and don't really go more than 45 mph around town. On the Highway, I'll run it up to 60, then I'll flip the O/D on.
I find that the O/D OFF keeps my rig from shifting into a final drive that is Not right for me.
Oh yeah, I should mention some specs.
'96 Geo Tracker, 4 door, 16 valve, Auto with O/D, 4 wheel drive. Calmini 3 + 3, 9" rear, Anvil front, 5.83's and Detroits, 4.23 to 1 t-case, and 32" MTR's.