According to the release notes:
The main thing to know is that you should 0.10.1. Otherwise, you will get booted off the network. If you are mining, make sure the pool you are mining on has upgraded its daemon. Only this version will work after the fork of January 5.
What is the worst case scenario if a pool or exchange does not upgrade in time and is forked off the network?
Would miners be at risk of losing anything other than the block rewards generated on the wrong fork?
Would users of exchanges be at risk of anything more than failed transactions if they send XMR to or from an exchange on the wrong fork? Could exchange users lose XMR?
How can a user of an exchange or mining pool verify that the exchange or mining pool has upgraded to Monero v0.10.1 - Wolfram Warptangent?