Why the change? Is this heavier than Spirit & Opp (which it resembles)?

It is quite a bit bigger. It can run over spirit. And yes, you guessed it, MSL is too heavy for the airbag deployment method. The viking lander which was heavy too used retro rockets. MSL is avoiding retro rocket use because they do not want to contaminate the landing site with organics from the fuel.

Here is a hypothetical picture of MSL next to Spirit:
http://www.nasaimages.org/luna/servlet/detail/nasaNAS~4~4~19199~123813:Size-Comparison,-Mars-Science-Labor

I'm really astonished that they would land it on it's wheels. That would seem to be risky. I'm also delighted to have one of these buggies in the wheels channel!

Moving this video to lighthouse's personal queue. It failed to receive enough votes to get sifted up to the front page within 2 days.

*beg

Sending this video to Beggar's Canyon to plea for a little attention - beg requested by original submitter lighthouse.

I'm surprised and really disappointed that you had to beg this at all. That was cool.

I was wondering why there were no solar panels on this behemoth so I did a little googling and discovered that they're going with a whole radioisotope decay thing. Plutonium: it's not just for breakfast anymore.