I used to buy low and mid priced ni-cad cordless drills and thought they were fine but the batteries didn't last all that long. Then one Christmas, my wife surprised me with a Milwaukee M18 Drill/Impact driver kit. It is unbelievably better than the older ni-cad models - more powerful, linger battery life, quicker charge, better ergonomics. I have had it for several years with much use and it still works like new. I use the drill ten times more than the driver due to the adjustable clutch.
These tools are absolutely worth the extra cost. I have subsequently added a circular saw, angle grinder and hackzall. I love my Milwaukee M18, but I am sure Dewalt and Bosch lithium ion are also good tools.