I'd like to add my tuppence in here too!
I thought that I wanted to feed my twins, but I was telling myself that if it didn't work, then I wouldn't. Little did I know how that attitude would change!
After a totally trouble free pregnancy, they arrived all of a sudden at 30 weeks (completely healthy, just small) so they were fed with expressed milk through nasal tubes. We started trying to get them to feed at about 33 weeks and eventually were sent home at 35 weeks - bear with me, this is relevant!
After a few weeks at home, things started to get a bit sore, then very sore, then excrutiatingly sore. After much agonising (physically and mentally) I called a lactation consultant who came in and diagnosed both of them with tongue tie. Once these were snipped, it made things so much easier.
Almost everyone kept saying to me, "just give them some formula" but I just couldn't. Silly really, when I'm sure that's what I'd suggest to someone else in a similar position. As with Kathyoi, it turned out that I was more stubborn than I had ever imagined. At times we were doing 24 feeds in a 24 hour period -a couple each were of expressed milk, although this lessened over time until I was fully feeding them at about 6 months (3 and a half months adjusted).
PrincessScrumpy, while I can't comment on having another child around, it certainly is possible to feed both and now, when people ask me - and then express amazement that I'm still feeding them now (at just over 1), I just tell them the truth, that it is just SO easy to do them together (with the aid of a feeding pillow) that it simply wouldn't make sense to stop now.
I had a mum of twins in my class who had said to me that it was perfectly possible, so as far as I was concerned, it had to be. For sheer convenience, it's well worth it.
Good luck - and sorry to hijack your posting like this!