As a former owner of a PBX-milled Viking I say that they are very solid, reliable and efficient markers that are easy on paint (with eyes fitted) and can shoot as fast as anything out there.
On the other hand, they are not exactly small or light by todays standards, nor is the milling particularly exciting.
All the above is true. As a current owner, I couldnt add much more. Very efficient, I aint that hot on tuning HP/LP regs to get the max efficiency out of guns, but I get at least 1000 shots, and people claim to get a case+ per fill.
Accuracy? Yeah, great- because there is very little kick, and also because it is so consistent (due to the high quality of its components) shot variation is very low.
Speed? Its WAS boarded, which is also user-upgradeable with a cable to the latest software. WAS boards are great boards, fast as hell!!!
Milling? Depends what you look for in a marker! If you like small, sleek shocker style guns, this aint it. What it is is a quality anodised, simple nice milling pattern. I personally like it, though I will say it has a certain military feel to it!
NOTE: yeah Skeet there are a few PL Vikings (as Im sure you know!) and PBX did one. Its not on PBreview, maybe its too rare? I dont know... You know the PBX people?