Hi nooschmoo...
The very small age gap between DC1 and 2 doesn't worry me too much at the moment as DS has been so very good - although I've probably been lulled into a false sense of security and it will all go horribly wrong!(ok, so perhaps I'm worried after all...) I don't think you can really know what it will be like, but we coped last time and will do so again! (OK, so the house will be dirtier...)
Other plus points for me are are I can back to back my maternity leave, DS will not really understand and get jealous (maybe), and they can play together later on. Negative point maybe that haven't recovered fully from last time and don't know it. However I feel like I bounced back very quickly so try not to dwell on that.
It is a bit different finding out 2nd time round though isn't it? I'm trying to be as excited but don't think anything wil be the same as the first happy/ panic feeling!
Tube travel - I used to get offered a seat at 3 months, so there are nice people out there - I think it depends on your line (go for the Victoria and Bakerloo!). Mind you it was 90% women and tourists who obliged (I took a running count in the name of research ), hardly ever men .