When I work the drill hard, like all cordless tools, batteries will heat up and drain quicker. The 20v has been better than my numerous 18v kits I've had in the past. Last longer, better Chuck, more torque. One big difference was the 18's would slowly get weaker, while the 20 I have seems to stay strong and then die abruptly. (Which I like)
There's a battery indicator on the back of each battery. 2 years later this old girl still holds a charge like a champ on unused battery in storage.
The reciprocating saw is also great. Use it primarily for cutting large copper conductors, aluminum cable tray etc while out in the field.
I was a makita guy for years but I've had really good luck with DeWalt. Some buddies don't like them but it's preference.
I'd say go for it.