I use poker office, but it's in essential need of a good update - a lot of stats missing that other software provides - how often player 3bets, call FCB(flop continuation bet), Steal blinds from small blind etc(is this a steal?). - update is expected for this summer.

Poker Tracker seams much more popular based on other forums hand histories etc, PT3 looks like it has a few teething problems with bugs, but will probably be great software later down the line, and I've heard good reviews for holdem manager.

personal preference stays with PO, but in reality they all do the same job, with HUD that give you loads of information.

If you don't have it - get it and spend time getting comfortable with it other wise you are bleeding money on both cash, sng and tournaments IMO. remember most other people at your table will be using the software against you!!