The battery to be specific. I can't find anyone who carries them any more, so I can't get a replacement. Or at least not easily. So why not take it up a notch:

Ryobi HP472K

SPECIFICATIONS:

• Voltage: 7.2 volts 
• RPM: 330/520 (no-load speeds) 
• Chuck: 3/8” keyless 
• Clutch: 24 position 
• Weight: 2.96 lbs.

FEATURES:

• Keyless chuck – enables quick and easy bit changes 
• 24 clutch positions – virtually eliminates screw stripping by adjusting for various materials and driving depths 
• Compact center handle design with power grip overmold – maximizes user comfort 
• Variable speed switch – controls drilling/driving tasks from a slow start to a fast finish 
• Built-in bubble level – improves drilling/driving accuracy by identifying the proper 90 angle 
• Forward/Reverse selector – conveniently located for inserting and removal tasks 
• On-board magnetic storage – for quick access to your driving bit

[ Ryobi ]

Didn't cost much more than the B&D tool I bought before, but has quite a bit more power. Plus it has 30 levels of torque to avoid stripping screws but still allow for the power necessary to get the job done. Didn't have a hex driver bit, but my B&D bits fit in the adapter just fine. And a tool like this is required for any Ikea project...