Looks, Construction Quality, Accuracy, Shot Consistency, Offset Hopper.
Weight, maybe a little front heavy.
I received my gun yesterday and handled it pretty much all evening. I put about 200 rounds through it so I've only really tested it.
Packaging: When I opened the shipping box and pulled out the marker's box I was impressed, BT packaging is excellent and presents the product in a way that makes you feel like you're getting a very high quality marker.
Looks: While at work yesterday I participated in a SWAT training scenario and was up close and personal with the SWAT team and their M4's. The BT-4 SWAT does an excellent job of mimicking the real thing sans the barrel shroud and front sight. If you are not careful with this thing an uninformed person may think you have a military assault rifle. This marker looks serious, it's all business, it makes my Spyder SE look like a flamboyant toy.
Feel: When I pulled this marker from its packaging the first thing I noticed was how heavy and solid it was. This thing feels like the real deal. If I needed to I could use this thing as a club and I doubt it would hurt the gun at all. There was a little bit of plastic flashing on the edges of the trigger and grip but I trimmed that with a razor blade and now it feels smooth with no sharp edges. Some may say the heftiness of this marker is a downside but I think it adds to the durability and realism of the marker. I do recommend a sling though. I also recommend a remote coil because the CO2 tank adds bulkiness to the marker and makes it less comfortable to shoulder. A final small complaint is that the marker seems to be a bit front heavy when the stock is collapsed and you don't' have the marker shouldered.
Operation: I put about 200 rounds through this gun in my back yard and was very impressed. Even with the short 8 inch barrel and cheap Monster balls I was hitting a tree with ease from about 100-150 feet. The gun fired very consistently and in a much tighter grouping than my Spyder does with a 32 degrees 12 inch Whisper barrel. Only 200 rounds went through the gun but I experienced no breaks, chops, or CO2 related problems.
I will update my review on this marker once I get a chance to play a few games with it.
This marker is excellent and you feel like a badass when holding it. All the good stuff you hear about BT appears to be true. I'm giving this marker a 9/10 because nothing is perfect and there are some slight improvements that could be done to help balance the marker's weight.