I shoot IDPA every weekend...sometimes 2 matches (one on Saturday, one on Sunday). I am the IDPA match director at our club and put on a match once a month. I am pretty lucky in the fact that there are several clubs in the area that put on monthly matches as well...and we have it worked out so that we don't interfere with each other's schedules. The down side...500 rounds a month gets pretty expensive now days (even reloading).
Training is by far the most important thing you can do...but competition is the best way to commit what you've learned to your sub-concious. When I first started shooting IDPA...I would now exactly how to draw, proper grip stance, trigger control, etc... As soon as the buzzer went off, it was like I suddenly became brain damaged. Under pressure, you will revert back to what's been committed to muscle-memory. But, this led me to identify defecincies. This would make practice sessions more productive, as I was working to improve a certain skill.
Now, when the buzzer goes off...I no longer think about grip, trigger, stance. Now those things just happen without me thinking about them. I compete with several LEOs every weekend, and they seem to agree that competition is the best way to keep your edge.
Just my 2 cents (after taxes).