Long time Reader of these boards, first time poster. I just wanted to say a few things that I've experienced with the Icon since picking it up in July.
Both my wife and I have the Icon, got them in July and we've both experienced many of the problems that a lot of people here complain about (spotty wifi, quickly discharging battery, etc). The difference for us is that we are on 8.0, we've never installed the developer preview on our phones. My first Icon was replaced because it wouldn't charge via USB, only wirelessly, otherwise that one seemed to work better than my current one. Both of our phones will randomly lose connection to our router or have a diminished connection, even though our other items (laptops, Xboxes, etc) are working fine. Heck, there have been times we've been we'll beyond where we should be able to get a signal (back yard at the fire pit) and it worked great, then other times where it should work (laying in bed directly above the router) and it doesn't.
I've experienced the quickly discharging battery on my phone where it gets really hot. I did a soft rest and that fixed it. Seems like something gets hung up once and awhile, no biggy... My wifes phone on the other hand has done this, and I have to do a factory reset. That fixed it for a few weeks, and now its doing it again, but without getting super hot. We've disabled all the background tasks etc, and she really has almost nothing on her phone to begin with, but it just keeps happening. Doing a factory rest and then not restoring a backup worked last time, but it doesn't appear to be a perminanet solution.
To me it really seems like there is something very faulty with these phones. I didn't own it before the Black firmware came out, so I don't know if these are new issues since then or not, but in its current state we are both very dissatisfied with the Icon. We love windows phone (I'm a previous Trophy owner) and the camera on the Icon is amazing. I have no complaints about the speed many others do, but I don't have other newer phones to compare it too, works fine for me.
Its taken since July until just this week to get the money deal sorted out with Verizon for replacing my Icon, so I'm hesitant to replace my wife's. It might be better for us to go into the store to do so. I'm hoping they give her the option to upgrade to the M8. Not because we dislike the lack of 8.1/cyan, but because she needs a phone that has a reliable battery...
Anyway, I just wanted to throw out there that I don't think 8.1DP is the cause of many of the problems as seems suggested, but it may in fact be the Black firmware (hopefully) or worse yet, a hardware issue (hopefully not).