Just thought I would add my own personal perspective on this one. Not trying to change minds or anything - just my 2c worth.
I have been pg three times with twins. twice was with IUI so no real choice in number of eggs released/fertilised. The third set was from elective 2 x ET - mostly out of fear of losing potential babies if nothing suitable to freeze.
As you can see from my sig - we don't actually have any twins! we m/c all in the first 2 sets (although It appeared 1 twin in each pg lead to the demise of the other). The last pg did lead to the birth of my gorgeous DD but it was a very complicated pg after the loss of her twin and she was born 5 weeks early - albeit very healthy in the end.
I still feel some sadness that some of those babies may well have gone on to be healthy children had they been singletons
All the lists of complications etc etc the IVF clinics scare you with are because they all DO happen.
The stats indicate that the actual overall live birth rate following double ET is not that much higher than with single ET. ie there may be higher chance of getting pg but there is also higher chance of losing one or both along the way.
I have no fear of actually giving birth to or parenting twins (would actually have loved to complete our family with twins last pg) but I am terrified of the extra risks and potential to lose babies which may well have survived had they been in utero on their own.
I totally get the desperate need to be pg ASAP and the practicalities of $$ (every extra cycle does put a strain on the wallet) but I have now learned to be a bit more patient and try to have faith that those embies that freeze will still have the same chance at success.