IDS is a good politician, and he pulls from the deal what he wants to justify his decision. He jumped based on one issue, but he is entitled to. However he isn't stating the exact truth, which is why I don't find newspaper articles like this much use as they will always be looking to justify his decision.
Looking at the actual document, we haven't agreed to anything in writing in terms of veto, the only reference is paragraph three here on page 14
http://data.consilium.europa.eu/doc/document/ST-1-2016-INIT/en/pdf#page=14 where we agreed to limit integration for those outside the Euro. There is nothing written in this document that states we have rescinded our right to veto.
Interestingly there are some great wins for Cameron in the document such as here http://data.consilium.europa.eu/doc/document/ST-1-2016-INIT/en/pdf#page=15 where we are not responsible in future for EU Euro member bail outs for instance.
I am not a Cameron fan, I think he could be tougher, but what do people feel about him, Boris or Corbyn being capable of negotiating all our future trade deals if you feel right now they are not capable of negotiating anything?