There seems to be two very distinct schools of thought on Dytacs. The first (which seem to mostly be early production batches) suggests that the gearbox is made of cheese and will explode on contact. The second (predominantly owners of later production models) have had no issues whatsoever. Their guns are accurate and reliable (I have a couple of friends that fall into the latter category).
Personally I've found them to be fairly well built although some do have fit issues between upper and lower receivers. Combat Series models which are the cheaper ones have the exact same internals but cheaper, generic rail systems etc. The ones I've personally had direct experience with have been well put together but the hydrodipped finish doesn't need much encouragement to fall off (moral of the story - get a black one). I liked them, decent rate of fire and range. I'd have one.
Land Warrior have been selling them cheapest but will not help with after sales support. Socom Tactical WILL service the guns and offer post sales support but charge more for the gun in the first place. There is some suggestion that the LWA pricing is a deliberate maneuvre to piss off the guys that run Socom Tactical but how much of that is true remains conjecture and potentially libelous so I'll just leave that there.