Airsoft has helped me tremendously. With a good blow-back style gun you have a suprising amount of recoil and can build all sorts of drills around them. Sights are moving just like a real gun so you have something to watch from shot to shot. Manipulation, etc is nearly identical to my STI's...it even fits the holster. I usually try and end with a little dry fire or reload practice with my real gun. This has transitioned really well for me into actual matches.
I use a Tokyo Marui Hi Capa 5.1. There are several versions of that gun available for as cheap as about $90. Several guys on the board have a WE Hi Capa 5.1. Those are all metal and very well built. I prefer the Marui because it is all plastic and the lighter slide actually means more recoil as well as uses less propellant. They are a bit more expensive, I believe I paid $150 for mine. When you handle one of the high end guns it becomes really apparent why they are so expensive though. Plus if you think about what it would cost to shoot 15000 or so live training rounds over the winter through a real gun, $150 doesnt sound like much at all.
Accuracy is reasonably good out to about 25 feet, which is realistically as far as you would ever shoot it in practice. With my gun I can just about put them in the same hole at 10-15 feet.
For targets, BAMairsoft.com has some really good scale plate racks, poppers, etc that are perfect for drills. They are great guys that shoot IPSC so they know what works for training and have developed some pretty cool stuff.
I think probably one of the best benifits was brought up by toyfreak. Going out to the garage for a half hour or each night takes a much smaller toll on family time that a trip to the range no matter how close it is. Also, knowing you can get a good practice session in when there is snow on the ground is a good feeling. In the past 6 months I have shot very few live rounds between matches relative to the amount I was doing when I originally started shooting USPSA. But I have been diligent with the airsoft/dryfire stuff and had very good success with it.
Make sure you are doing the RIGHT kind of practice and not just spraying pellets around though. It is very easy to take the fact that those pellets are practically free and start screwing around. You need to treat it like it is a real gun shooting real bullets and make your shots count like you would in a match. If you havent taken a class from anyone yet, pick up a copy of Mike Seeklanders book. It is full of excellent drills that you can implement with an airsoft gun and keep your practices productive.
