Cleaning it should help if the D-Pad is sticky.
I've never had this problem on my Wii. I did on my N64 and cleaning worked.

I just bought 2 new Wii remotes with very unresponsive D-pads. Only in my case they weren't worn out, they were crappy to begin with. I have to apply a lot of pressure before they register, which causes very aching thumbs.

I'm contacting the online store that sold them to me, I want my money back, or replacements.

wait, you only have one wiimote? Wii is for Multiplayer!

You scared me... the title suggested there would be a wii-mote redisign

my d-pad is like that, but my b button is. it takes a lot of pressure to push down all the way, and it seems kinda sticky.

also the r button on my ds did that, but it was just a poor victim of my constant mkds playing.

I have not had any controller problem -- thankfully.

Unfortunately, you might have to buy a new one to solve this problem.
If that is the case, take two since they are small.

Mike from Morgantown

The rubber grip probably traps dirt and sweat in, because I never use the thing and my controllers have never been remotely close to very dirty.  I've had to clean up smudges and such before, but that was a simple wipe and it was clean.

I do want a wiimote redesign :( the control pad should be bigger and with a different texture, something like the DS or the SNES maybe