Ion Cannon is OK in my opinion. With the cost reduction, it is now more or less a usable commander power, but it is still hard to micro it precisely. It needs a lot of practice and good situational awareness, which in my opinion is much more fun then brainlessly stealing pads with Liang drone. Base damage would need a review, but Solomon ion cannon base kill is still hard to be achieved. Since the patch, I have been matched with maybe 2 opponents who used ion cannon with an actual plan and nobody attempted a base kill against me.
Oh yes, and if your opponent has a chance to use it 5 times in a game...well it rather shows that you are doing something wrong and not that ion cannon is overpowered.