The Wiis main drive isnt a CD one.(Dual layer DVD)(cant play DVDs without a hack)
Also as a set top box the Wii is rubbish (even if fully working)
-Its browser wont work on all sites
-No TV card for watching normal TV
-Small hard-drive that cant have programs saved on it
-The mentioned lack of DVD playback without a homebrew hack
For the same price as a Wii you can get a cheap PC that will work out better as a media centre.