i have used a few and seems like all they want to do is change the backlight settings and also the radio settings so when your in a low coverage area or roaming it turns the radio off.
they work good if you use them for all their worth but i find that it impacts me more to have the backlight turn off after 3 seconds and i dont roam alot so the radio stuff doesnt help either.
i bought 2 apps for my blackberry 9650 and then just waited for seidio to release an extended battery and ive been happy ever since.
These apps are a waste of space. If you remember to do a few basic things, it will also save money. Reduce you screen brightness to 30%. Close the apps that aren't being used. Don't just hit the back button. The same applies to browser pages. For apps that run in the background, change update interval to manual or the longest interval.