While the mobile phone industry buzzes like a beehive about Ice Cream Sandwich and all of the shiny new devices designed to run the latest version of the Android mobile operating system, I'm discovering that a couple of old phones from 2010 run the new software brilliantly - no purchase necessary.
My phone is an HTC Desire Z, better known in the US as the T-Mobile G2. I never ran the stock software on it at all; it was rooted and reflashed with CyanogenMod 7 as soon as it came out of the box. (It's a decent phone, although I probably wouldn't purchase another one or recommend it to anyone else - it doesn't have quite enough RAM and the Z-hinge keyboard design makes it heavy, bulky and unnecessarily fragile. Honestly, I think I'm over the need for a physical keyboard now; soft keyboards have improved dramatically over the years.)
I've been waiting anxiously for CyanogenMod 9, the new major version based on Ice Cream Sandwich, since the Galaxy Nexus was first released in October 2011. Unfortunately, CM9 has been a long time coming; it's April now, and the developer releases are still alpha quality, although I expect things to start shaping up quickly with the advent of their brand new build infrastructure. With that said, not all is lost: their open source code base is frequently adapted into unofficial builds, and some of these are impressive indeed.
Enter Andromadus, an ICS ROM for the Desire Z based on CM9. I've been running it for a few weeks now, and I'm quite happy with it so far. Although Beta 1 had a couple of ugly glitches, Beta 2 is really quite stable and does everything I need it to do. It does spontaneously reboot from time to time, but I'm not sure how much I can really blame the ROM for that; the phone only has so much memory, and I push it awfully hard on a daily basis.
Next up: the T-Mobile myTouch 4G, my mom's phone. Although she was perfectly content with the stock firmware for two years, she recently changed carriers and the extensively T-Mobile-branded software suddenly became very unhappy. Third-party firmware to the rescue once more: the interestingly-named Zips Creamed Glacier is another ICS ROM based on CM9, specifically for the myTouch 4G. It loaded up quite smoothly and seemed very fast during setup, and although I haven't spent a lot of time using it myself, I haven't heard any complaints yet.
In conclusion: if you're interested in running Android 4 and already have a decent handset, then you might just be in luck! Although the CM9 alpha ecosystem seems to be a bit fragmented at the moment, I am hopeful that things will start to converge in the near future; all indications are that, when CM9 becomes stable, it's going to be great.