I've had Android 4.0.4, the Ice Cream Sandwich implementation, on my Droid Bionic for just over a week, and I am pretty happy with it. Some of the positives:
1. Android 2.3.4, which came with the Bionic, was pretty poor about holding 4G LTE connections. Facebook was notorious for knocking down the 4G LTE service, and my local Wifi connection uses a broadband carrier that provides much slower services than Verizon's 4G LTE network, so I was looking for a big improvement. Ice Cream Sandwich gave it to me.
2. The 4G LTE service really sucks battery life QUICKLY. 2.3.4 had few provisions to reduce this tendency and the Bionic has a battery that is not very well equipped to deal with it. That's still a problem with the Bionic, but at least there are some services that ICS makes easier to use to help automatically put processes to sleep that consume excess battery power in the background.
3. The appearance is pretty good, and most of the features are convenient. A few of the new swiping mechanisms, being quite a bit different, take a little getting used to, but once learned, are as easy as before, and several of them are more convenient.
Overall, the ICS upgrade is a rather major improvement over Android 2.3.4 and anyone with a Bionic would be very wise to take advantage of the upgrade. It is a BIG one, though, and it takes quite a while to even download, and quite a while to install. Do it when you can afford an hour as it installs, and give it overnight to download.