Sorry to resurrect this - I've been on holiday! Just to respond to Ruth...
Getting the leave regime right is part of the picture - eliminating the pay gap is an essential other part - I work with the EOC on this issue - for me the pay gap is a pain in the arse - it limits men's caring opportunities.
The inequality in leave worsens the pay gap (women out of the labour market for so long compared to men) and the pay gap leads to couples deciding that the woman should do the childcare and the men should do the earning.
It's interesting that in the UK now (according to the latest research - my source is Dianne Houston from Univ of Kent) that if couples are offered a "money no object" choice of different divisions of labour (e.g. man working full time, woman at home, man working, woman working part time etc...), the MOST popular option among british men AND women nowadays is:
Man AND woman both working flexibly and both sharing childcare.
Interesting, eh? I think current policies are failing people's aspirations.
In European countries with more progressive leave regimes, things are better - Swedish dads are much more involved than UK ones for example, but there are other factors - e.g. in Holland tax on second incomes are v high so hardly any women bother working. So you have to get the whole situation right to establish a level playing field for men and women with regard to both work and caring opportunities.
RE: gay families etc - I was asked this when I sat on the DTI's committee looking at the implementation of paternity leave - what about female partners of women giving birth. My position has always been that whatever fathers are entitled to, they should be entitled to as well. So if we had a transferable system, or a parental leave system, they'd get the same.
It's easier for lesbian couples, cos one is generally giving birth, and the situation is similar to a straight couple. However, the biological father may be involved. Under current legislation, I would say that the female partner and the bio father could BOTH take paternity leave if they were going to have a role in the child's upbringing - that's how I argued it in committee.
For gay dads - it's much more complicated, as I'm sure you know. It comes under adoption law, I think?
Adoption leave really shows how ridiculous the current situation is - one parent has up to a year, but the other can only take 2 weeks. And neither have given birth, so there's NO question of recovery from birth - I think it's ridiculous, and forces couples into a primary/secondary carer model, whereas the most popular option these days is for shared care.