I do alot of concrete pad prep for commerical flatwork mainly < 100,000 ft. I have tried various laser grading systems to bring the grade to +/- .25". In my experience alot of the accuracy of the pad is determined by the type of material your working with, i.e. mixed soils, clays, etc. are much harder to get to a tight spec even with a lazer so I keep that in mind when bidding. I primarily use a JD 450H dozer with a single pole mount Topcon receiver for rough in and a Cat 277 with a dual pole Topcon automated box blade for final, usually on cushion sand. I tried using a Bobcat brand grader attachment but it was expensive ~$10K and didn't do as good a job as the box blade especially in hard materials.
I use a single slope Topcon laser since most of my work is either flat (pad) or on a single plane. I have demonstrated the dual slope but very few jobs required it, so I avoided the extra cost. Most of the time if the job wasn't flat or single planed it was full of complex grades i.e. parking lots sloped into multiple drains etc., which makes any laser system short of 3D useless.
If I had it to do over again I would setup a dozer with a single pole manual receiver for rough in (~$1800 receiver, $200 pole, and a little welding for the mount) and buy a small grader for the dual pole automated, and drive them with a single plane laser. Instead of putting the ~$7500 for the automated system on the dozer and $10K for the skid steer, which still has a hard time getting .1" even with multiple passes.
The reason I stated I would rather have setup a small grader (ie. Fiat Allis) with a two pole automated is that the machine will be capable of far greater accuracy than any skid steer with grading attachment before you even strap on the laser system and it will allow you to cover much more ground than a skid steer. The grader will also allow you do fine grade work for jobs like parking lots and roads with complex grades where you can't use your laser system. Also, the operating cost per foot of ground covered in a track skid steer is many times the cost of the small grader even though they are more expensive to purchase initially. I was amazed when the Cat dealer told me the tracks on my machine were $5000 just for the tracks (no labor, rollers, etc.) and they would last about 2500 hours in ideal conditions! Given that your probably going to spend $10K-$15K to setup a fine grade machine I'd make sure it could service the largest body of work even if it didn't use the laser. Of course this would be moot if you're doing a lot of inside work as you mentioned above.
I guess the bottom line is that I consider a basic laser system (single plane with a manual single pole) invaluable in pad building, but the returns deminish quickly when you start spending the money for the really accurate setups unless you have the right machine and you're doing a lot of specialty work.
