None! (dont let others convince you its too "heavy")
For a woodsballer like myself (and all other woodsballers for that matter) the most important feature that I look for in my marker is reliability. I need to know that when I am in the heat of battle that my marker wont chop paint. I need to know that whether I am on a dead sprint or playing in windy rainy conditions that my marker will function without a hitch. Well I present to you the BT Delta Elite, this gun is reliable as it gets my friends. Why you may ask, well it begins with the solid BT-4 design. One of the first things you will notice when you hold this gun is how solid it feels. You feel more like you are holding a gun and not a toy like most of the other markers out there on the marker today. I actually prefer the weight of the marker for this very reason it makes the marker more durable. Some might complain about the marker being too heavy but this is only an issue if A) you are small in stature or B) you dont use a remote line. I very highly recommend getting a remote line for this marker otherwise the weight will become an issue if you plan on playing for long periods of time.
Now onto a key reason why I have found this marker to be so reliable, the Rip Clip. Which is a sound activated feed system that comes standard with the BT Delta Elite. Unlike the cyclone feed system used by the Tippmann line of markers the Rip Clip is extremely reliable. I have fired thousands of balls through my Delta Elite without chopping or shredding a single ball! And believe me when I say that I am pretty rough with my marker when I play. There is an "eye" in the Rip Clip which always keeps it in perfect harmony with the E-Grip, thus preventing you from shredding any paint in your marker. If you have had any doubts about the Rip Clip please take my word for it, it is the real deal. The Rip Clip is more than capable of rates over 20 BPS which is more than enough to keep up with the 13 BPS that the E-Grip will provide.
When I first read about the Apex barrel system I was very skeptical and frankly it sounded like a gimmick. But after playing around with it it out in the field I found it functional and I look forward to experimenting with it some more. One thing is for sure the barrel is very accurate and you will be surprised by how far you can break balls with the barrel on this marker!
The Mil-Sim look of this marker gives it some very nice styling points which for me is not extremly important but its nice to have and it certainly enhances your paintballing experience. The MP5SD style shroud that they put on the marker is actually very functional as it gives a nice solid area to grip the marker with. I am a fan of the retractable stock that comes with the marker, I was concerned that it would feel very flimsy but I was surprised by how solid the stock felt when fully extended.
For those of you looking at just the BT Delta instead of the Delta Elite I highly recommend getting the Elie. It is a MUCH better value than the Delta. Features such as the Rip Clip and the E-Grip are must haves in my opinion. If you decide to buy the Delta keep in mind that you are buying an inferior product to the Elite. If you buy the Rip Clip, E-Grip and Apex system separately you will have spent more money than if you just had purchased the Elite in the first place.
I obviously very happy with this marker. Although for some it might seem pricey but you get what you pay for. Try it out you not regret it. I give it a 10 cause I simply couldnt find any faults with the marker!