I don't think there ever was a PCI-E 1.1 8800GT. Was there??? Anyway, it doesn't matter - the 8800GT works just as well on PCI-E 1.1 and PCI-E 2.0, no difference.
P45 - I don't know, honestly. I still like some P35 MBs more. For example the GA-EP35-DS3R has 3 PCI slots and 8 SATA ports, while the GA-EP45-DS3R has only 2 PCI slots and only 6 SATA ports. If you need a sound card/TV tuner/modem for example, it's annoying to have only 2 PCI slots. You can buy USB based versions to solve it, but they cost more. If you want 5 HDD and 2 burners, only 6 SATA ports are also annoying. OK, maybe it's just me.
Interesting article about overclocking the P45. I think the point is if you overclock a lot you need to know about a lot of weird BIOS settings and to spend a lot of effort and time. Well, that's fair IMO and to be expected. For your average enthusiast who wants to overclock but doesn't care about records, I think the P45 is just fine. Keep in mind that a P35 (normally at 333MHz) gets praise if it can do, say, 420MHz, while a P45 (standard 400MHz) gets insults if it only does the same. The P45 may in fact get you a higher clock than a P35, it just doesn't blow past expectations so nicely because the expectations are higher for it.