Picked up the other two ultimate build sets to go with Mater - McQueen's top half is connected in a very interesting way and Francesco is kind of plain on his own but would be the easiest to convert into a regular car.
My daughter loves them all, although McQueen is by far the most solid of the three and Mater is her favourite to play with due to the tow hook.
The downside is that putting these together has gotten me back into Lego, and looking through all of the sets on the market right now has given me a ton of ideas.
And unfortunately (for my wallet), Toys R Us has the Millennium Falcon on sale this week ($155, down from its $180MSRP in Canada), which is the one Star Wars set I'd actually want.
How big is it, though? I checked the box in store earlier but it didn't give any dimensions and I don't have a ton of room in my apartment. I'd guess maybe a foot in circumference but I'm not really sure.