I think there's a really good case for extending maternity leave for people with premature or disabled babies and for increasing benefits (e.g. to cover the travelling costs people with disabled/prem babies often incur), just as much as I feel that people with multiples could do with a bit of positive discrimination. I don't feel it's a good idea to object to help for person A simply because person B is equally as deserving. Hopefully we an improve everyone's lot one step at a time.
That said, as a mum of twins, I would like to make a few points.
Having two or more newborn babies is very different from having one, even when there are other children (sometimes only 9 months older) in the household, especially if you're breastfeeding. That said, once you get past the endless feeding/changing routine and start getting some sleep again, I think multiples can actually be easier than having two of different ages, though that's just a personal viewpoint.
There are some financial implications though, which are specific to multiples. If you have two children close together, you get the 'child under one' element of the tax credits for each child (unless you got pregnant straight away, in which case you'd miss three months worth of payments). If you have twins or triplets, you only get it once, as you can only claim for one child under the age of one. That's not fair.
You also can't hand anything down with multiples. I know there are plenty of families with small age gaps between their children, but at least they have a bit of time to save up some money from the time they bought child 1's car seat to the time they have to buy child 2's car seat. With multiples you have to buy everything all at the same time. With triplets it is even worse as the equipment becomes more specialist and therefore much more expensive. A double buggy, for example, is commonly used by parents with different aged children, so parents with twins can get one at a reasonable price. Triple buggies, however, are not as common and are expensive even on the second-hand market.
Childcare is another issue. It costs the same to put two children into nursery regardless of whether or not they are twins or different ages. The difference is that with singly born children you have longer to pay the full amount. For example, if you have children with one year between them and you start both of them at nursery when they are aged 1, you will be paying out for 4 years (assuming they're born in september). Child 1 will have a year, then both will attend, then child one will leave to go to school and only child 2 attends nursery. With twins you are paying the same amount of money but in three years. It's a bit like repaying a loan in 3 years instead of 4. It's also next to impossible to find a childminder prepared to take on twins under one, and many childminders only ever have one place at a time newly available, let alone 2, or 3 or more.
Now that my twins are older (just turned 3), I rarely think of them as twins anymore. I don't feel any different to any other mother of two children. I certainly don't feel that my life is harder because I had multiples; quite the reverse in fact.
Anyway, all this is a digression from the main point of this thread, sorry.