At least with a nanny share, you don't have to get the children up, cleaned, dressed and fed before dropping them off.
I did a nanny share for 3 and a half years, it worked very well, although back then I wasn't very good at taking my holidays so it made it easier for the families to take holidays (in my reference from one family it says they had to make me take holiday!)
I did a week in each house, the children from the other family would come in the pj's, I would get them all washed dressed and breakfasted together, was good for the children to see the others behaving and being praised when they weren't being very co-operative!!
I would also bath them all together at the end of them day and back in pj's (there were 4 under 4 at the end) so parents could spend an hour playing with their children when they had picked them up.
Also, the families would leave a change of clothes/bottles/pj's/nappies etc at the other families house and replace when needed. The families houses where only a couple of streets away so if anything was forgotten, I could pop in on our way out/home to pick up anything we needed.
Was also fantastic when the families expanded as when MB's were on maternity leave we just stayed at the other families house for the duration, pregnant MB got rest and we got peace! There was a 3 week overlap in maturnity leave but was in the summer so we were out ALOT!
The only downside was communication, one family would either talk to me about changes or the other family, I think we should have all sat down together to discuss any changes, all of the changes involved all of us so should have been agreed with all of us. She would ask the person she thought would agree easily!!!!
Also, she wouldn't turn up to pick up her children if it wasn't convenient, i.e. I had to have some dental work done, I tried to book it so it didn't affect them but there were two occasions when I had to go during work time, I phoned and told her and also wrote in the book that was in her child's nanny bag for notes back and forward that I had an appointment and could she arrange for someone to collect him for about an hour and I would pick him up after the appointment but she just didn't turn up or answer her phone (was in a meeting apparently) so other family mum had to look after her child, with no apology or thanks, which I thought was very rude and made things strained for a while.