I compared pinouts myself and the only difference seems to be that the newer chips have more functions on top of the Atmega8 functions. The trouble is that Mouser is out of Atmega8 chips and will be until July. If I have to buy the parts separately I need an MCU. If they come with I don't have to buy any MCUs.
The serial boards are great for my needs. I really just need a circuit board already made up with the lines brought out like that. It even has a ground plane for the analog lines. I don't want to have to send another order and I don't want a lot of extra parts.
I built an ISP from the old Ponyprog schematics on Lancos. It works. I have an Attiny26 happily flashing LEDs now. My application wants a couple of analog inputs and the Attiny gets crowded if I can't have the same port switching and watching three analog inputs. I think it will also want that ground plane.