So a double spend would have to be performed at the exact same time? So even if you waited a minute for one confirmation then what chance is there that the double spend will succeed?
You don't have to send the 2nd transaction at the same time, but the longer you wait, the least likely it will succeed because the original transaction will probably have more traction.
Trying to double spend after 1 conf would be pretty difficult. You can query blockchain.info & see how often orphans blocks happen. I think last time I looked at it, it happened like once or twice a day. So basically that means you'd have to be double spending right around that off chance that an orphan gets generated - which you won't know until the next block (another 10min).
Then you have situations like the 0.7 vs 0.8 fork that allowed for 100+ conf double spends depending on which version you were using vs the person you were double spending against.