I have never used any poker tracking software while I am playing online. Does it give you an advantage or help your play? If so, do you have a type of software you prefer and if so, why do you prefer it?
Most of the "cool kids" (including me apparently) use Holdem Manager. Very stable, tons of stats. The reason we use it is because we all multitable (6+ tables at a time) and it helps us tremendously in tough spots. It's fully "a-okay" with poker rooms too. As an alternative you can try PokerTracker3. Both software have trial versions for you to experiment with.