We really should differentiate between ICS and the stock ICS update.
I am rooted running the ShoStock2 ROM and I couldn't be happier with it. It's fast, smooth and the battery life is double what I was seeing with gingerbread 2.3.6 stock. I haven't had any problems with call dropping, SMS or MMS, GPS, HSPA+. I keep wifi and bluetooth on almost all the time and sync with four mail accounts (2 gmail and 2 pop).
I really haven't had any problems with it. Maybe it's the apps I use, or more specifically don't use.
Here's the list, if you'd like to check it out. No memory issues, either.
For those of you running the stock ICS update and aren't thrilled, I really would recommend a complete wipe of your phone. It will take a little time but it will make a big difference.
First, backup your important data, then back up your important data. Did I mention backups? You know you should be doing that anyway. If your apps and contacts are sync'ed to Google, then they will be reinstalled after the reset. What you need to watch out for is the SMS database. There are several good SMS backup apps around, just find one that works for you.
Once you've checked to make sure everything is backed up OFF your phone, as in on a PC or removable drive (not just your sd card), and then checked again, perform a factory reset and reformat your sd card and internal storage partition.
What this will do is clear out the caches and get rid of any incompatible gingerbread files lurking that are notorious for causing problems. It will also assure that your apps are the latest ICS versions.