The orb option is good enough that there are people who believe that not only should you keep Sleep from levels 1-30, there are even those who think you should have a higher Wis than Int.
I'm not one of those people, but it is an extremely powerful effect... and really, the only other choice is to invest in Con. You do get 2 points at every stat bump.
At low levels, keeping cloud of daggers going an extra round each encounter can easily be worthwhile, especially if you have a tide of iron fighter or positioning strike rogue. You can really play ping pong with those two and thunderwave...
That said, I'm not big on either the sleep spell or the tactic, but there is a valid reason people like it.
It is the only control class feature outside his powers the wizard gets, and all