Um... I would definitely NOT download the developer preview. My phone was rock solid with killer battery life. Now? Not so much.
When I press the power button, it won't come on. This happens a lot. Sometimes you can hold the button down and it will give you the power off screen, sometimes you just have to wait until it decides to work for you. I can't handle this.
Sometimes... (Quite often compared to NEVER before) It will all of a sudden get rocket hot and the battery will start draining like crazy. This phone had the best battery life of any WP I've ever had. Trophy, 8X, 822, 928, Icon. I've got plenty of experience to judge from. Overall I'd say I get roughly half the battery life I used to get.
The screen dances around when scrolling.
General sluggishness.
I'd say ruined would be my experience. Some of the features are nice, but wait for the official release and don't ruin the best WP Verizon has ever put out. As far as the Icon goes this release is very much a Preview. I just hope the final version fixes everything with official drivers and Nokia repairs.
P.S.
WiFi is seriously broken as well. If you do go ahead with the update, don't judge the WP experience by this Preview