The other reviews have got it right. But here goes anyway.....
This cable will connect your wii to your hd tv, but you won't get an hd picture. Your wii only produces a standard definition picture. What it will do is allow you to connect a progressive picture instead of an interlaced picture. This is one reason i bought the cable. On my hd tv the inlacing artifact (non-alighed alternate lines) dissapears, as you might expect. You will need to change your wii settings to do this though. But! In progressive mode the wii only produces 480 lines as opposed to 576 (pal) lines in interlace mode. So you have a lower resolution picture that your tv must scale even more to fit it's native 720/1080 lines! This gives more scaling artifact (jagged edges in the picture).
Overall this cable produces no better a picture than my wii scart cable, which only supports interlace mode (at least on my tv). It is 3m long though; the other reason i bought this cable.

This product is worth it if you have the money to spare. It provides 480p not 480i, so it is High Definition, and the *sound* is also improved not just the picture.

Picture is about 20-30% sharper with this cable and as I say, the sound is also much better!

Seriously this makes no difference on a TV over 32", I bought one and used it on my 37", what a waste, this picture is almost the same, on smaller TV's this would make a slight difference, such as slightly sharper lines, but just because this says component, don't be fooled this is in NO way Hi Def, it outputs at 480i, the defination of HD is atleast 720p and FHD is 1080p, and this like I mentioned is not even close.