The two big boys (Holdem Manager and Poker Tracker) both offer free trials. I'd definitely recommend using one trial and when it expires use the the other. I think PT is 30 days for Hold 'em and 30 days for Omaha and HEM is a 60 day trial. Once you've used both just choose whatever you feel the most comfortable using. They both have their pros and cons but they're both way better than anything else on the market. Personally I like PT4 better but really it's all about what you feel more comfortable using. Taking full advantage of the trials is invaluable to making the best decision for your game. You might find if your just playing on Carbon, and all your really looking for is the HUD portion and not so much of the back end analysis of statistics, that you are fine just using the hud they provide