We are avid train fans, and I waited to buy Ticket to Ride until my kids got old enough to play it (6 and 9, no problems aside from the little one's occasional struggles with the concept of playing fair.)  The playing time can run a little long -- not unlike traditional Monopoly, which sometimes is a fast affair and sometimes drags out.  But we have thoroughly enjoyed Ticket to Ride since Christmas, and already have expansion packs on the birthday wish list.