The original post lacked info for "regular users".  Here it is:

(1) If you are a "regular user" (not a miner), the best thing is to do nothing and wait a couple hours.
(2) If you are a "regular user",  Upgrading, downgrading, whining, FUD, etc, will make no difference.  Only miners have an incentive to do anything.
(3) Regardless of who you are, your transactions are not dead, your coins are not lost.  They will just temporarily be held up.  If you sent a transaction within the last few hours, it may take a few more hours before it's sorted out.
(4) If you insist on processing transactions right now it's probably best to wait 30+ confirmations.  It's just due diligence though ... an attacker would still need a tremendous amount of mining power, quick thinking, and a victim willing to part with a lot of BTC.
(5) By tomorrow this will be in the past and everything will appear to be normal again.  If you slept through this, you'd never know that anything happend (except for the price drop).

Let me reiterate, your coins are not at risk, your transactions are not lost.  It'll just take some time for the network to "iron itself out."  Everything will be okay.