yes -- I've done it twice on a samsung galaxy note. First time was because I immediately realised that ICS was not worth having to charge a second time; and the second time (of upgrading to ICS) was just stupid, because it had the same battery impact.
The difference in the battery usage was phenomenal -- on GB, I use it carefree all day (I'm a heavy user), and end most days with 30%+ in the remains. On ICS, even after deleting applications that I think might be heavy users, I can't go a full day without a recharge for about an hour.
When I go back to GB (which is a complete reformat, remember, so all apps needs to be reconfigured), I get the 70% usage per day back. There is no doubt in my mind that ICS drains the battery a lot more than GB -- in my mind it's a 2x difference.
For disclosure -- I am a very heavy user and I have two mods which might also have an impact: (1) I use an oversize battery (+50% more mAh), and (2) I use Juice Defender Ultimate with extremely conservative settings.
Therefore, it's possible that my awful and repeatedly poor battery experience with ICS is because (i) the battery mod is incompatible which seems unlikely or (ii) Juice Defender can't do the same controls on ICS.