We bought Rush Hour Jr. for christmas for my 6 and 5 year olds.  They loved it and were on the most advanced level really quickly.  Even my 4 year old could do it.  We just got Rush Hour and it's even better.  I don't know that there is much reason to get the Jr.  My 4 year old was able to solve her first card (on the regulard version) right away, so there is plenty for kids to do on this one.  I love it as well. The advanced cards are pretty challenging.  I think it's a great educational toy that is good for children and adults.