The derp KV is now my favourite tank. I use it as direct LOS arty when I can - the 152mm is very powerful and suprisingly, very accurate. I don't believe the written stats on it - I've hit nearly everything from 300-400m away.
The derp KV is my favorite tank to play also. I've had it for about a month now and this is the first tank I've gotten where I didn't feel over matched and somewhat helpless (where you feel your tank has a pea shooter relative to the tanks you are facing) when tossed into the higher tiered matches.
The derp gun makes this tank effective for any tier battle it gets thrown into. As suggested by an earlier poster, your earning potential goes up the higher the match tier. As such, I look forward to those matches more when driving my KV. It's more of a challenge since you're facing better tanks (bigger guns, better armor, and better speed) and more seasoned players, but I find that more satisfying than driving around and one shotting clueless newbies. Also, team play is a lot better at the higher tiered matches.
From what I've seen, the derp is more effective in laying damage with its hit than many high tiered tanks can put on each other. They are doing the high tiered pew pew pew on each other (nicking damage points off of each other) while you can lay a derp bomb that chews off big chunks of damage. As such, a lowly tier 5 KV derp can change the direction of a tier 7 to 9 battle if played right.
As for accuracy, I don't have too much problems with it and I generally expect to hit most of my short to medium distance shots with it. The secret may be to aim very carefully so the reticule is as small as it is going to get (and maybe waiting a split second longer). It's also important to aim when you're point blank as I've missed hurried shots thinking I can't miss this close with the target filling the reticule. The smaller the reticule the more accurate the shot and also the more effective (better hit points). As mentioned, long distance shots are possible too (I'm thinking maybe a 50/50 thing) and I always take them if the opportunity arises. My longest was a 560 meter hit across the map.
The long reload is a handicap, but you just have to work around this weakness. Work close with teammates so that you don't get overrun when waiting for the reload and keep cover close to you since you don't want to be exposed during the reload.
Even alone, you can compensate for that. Last night I was the last tank left with my KV derp against seven in a tier 7 match and managed to take out six of the other tanks before losing to the last tank that capped before I could. I took out two other KV's and a VK3001 all one on one (all were 100 percent except for the first KV). I then took out a group of tanks consisting of a T29 (only at 30 percent health -- but still a worthy opponent) that was supported by a panzer iii/iv an a panzer iv (both at 100 percent). I one shotted each of the KV's and two shotted the VK, but the last group took me at least 6 shots with the long reload between each shot. Obviously, in that game, the tanks I was up against didn't take advantage of my derp KV's weaknesses (any of the tanks I didn't one shot could have destroyed me while I was waiting for my reload). That makes for another good reason to play one as you get a better understanding of these weaknesses so that you can use it to your advantage when playing against it.
It may be my favorite tank to play, but it is also my most hated to face as being on the receiving end of a derp isn't much fun. As such, it's going to be the tank I make note to kill first if I see it at the other end of my sights (no matter what tank I'm driving). I think a lot of tankers have that feeling, so if you are driving a KV, you have to stay behind cover and be sneaky with your shots to survive long in the higher tiered battles.