X1 also has matte screen instead of reflective, which might be huge plus, if you intend to use the laptop in areas where you can't control the amount and direction of light.
On the other hand, mini1012 (newest mini10) with Atom N450 has over two times longer battery life (my X1 used to get 4 hours of practical battery life, when battery was new, and 1012 should get 8+). Then again, if 4 hours is enough, X1 is really good, especially when upgraded with SSD (1012 has better selection of SSDs you can get though, because 2.5" form factor and SATA). 1012 can be upgraded to 2GB too. I still prefer the X1, I actually have two, second one being spare parts/reserve