Yes, there are small pieces so you have to count your marbles (catch the pun?) and make sure they are all accounted for. I think four at a time is enough for normal play.
For the Little Guy's birthday we wanted to find something he would enjoy for hours, not minutes. When looking around online we came across this marble tower. I remember having one as a kid and loving it. It wasn't nearly as fancy as this one but it was just as much fun!
The most difficult thing about this toy is sitting back and letting the kids play. It is so tempting to take over! After bedtime I have my fun and leave a newly arranged tower to be "tested" in the morning. The only thing I can think of that would make it better would be getting a 2nd set for Christmas!