I switched from D300 to 5dII half year ago. SO...
-turn off Nikon's AF small lamp which supports achieving focus in low light and u will have smth similar to canon 5d2 AF.
-AF is not good to be honest in 5d2 (crap in low light)-it just cannot achieve focus even in center point (in LOW light).
-Image quality and resolution is far more better in 5d2. Quality is superb in my opinion with good lens of course. Cropping abilty due to resolution-WOW!
- ergonomics is far more better in Nikon, i have still problems using canon, it's not so intuitive as Nikon
-exposure meter is very good in Nikon, S___ty in Canon in my opinion or my 5d2 is a problem (sent it to service but they stated everything regarding built-in light metter is ok)- i have underexposed images in 5d2.
- so...after a while working in studio with canon I looked at nikon photos...OMG...where are those details I thought! I don' like most things in Canon, but on the other side I have to admit that quality of photos is really outstanding and not comparable to Nikon D300
-one more thing-Nikon has a lot of parameters u can set to fit your needs. Canon has very poor menu, u just cannot customize it in similar way to Nikon. It's limited in that area. For me, taking photos with Nikon was"easy"- good AF, good exposure meter, fast, reliable, has good built quality-i miss a lot of those things in Canon BUT...if u look at IQ from 5d2 it's hard to go back to Nikon's 12 MP. I don't know how far u go with post processing but there are also differences in that area. Maybe i was used to Nikon NEFs but i prefer them to procces, I am under the impression that I could achieve more from dark NEFs then from dark CR2s but, after getting some experience things might change. Another thing regards studio shooting-X-sync in Nikon is 1/250 which works in studio, Canon x sync is 1/200 but my 5d2 works with studio strobes only up to 1/125.
Canon is more "risky" when taking photos let me say and sometimes it leads me to frustration, but final result could be better than with Nikon. Nikon is camera which can be trusted but final results (IQ) is good or very good but not outstanding as from 5d2! Hmmm...having and using Nikon is like being married for 10 years with nice wife, using Canon is like having a sexy lover from time to time
Hope it will help a little bit.