Mike while your design is smaller it does sacrifice a lot of usability without a silkscreen layer to help identifying pins. And while I recognize the Pico is only a fraction of an inch smaller it could be argued that your om328p is also only a fraction of an inch smaller.
A couple other design notes and responses... Im not really interested in legacy compatibility with the Basic Stamp. I think for today's users and the types of things I see artists, designers, and students doing, legacy support is more of a hindrance. The Pico features all digital i/os on one side with the analog and comms on another. This mimics the simplicity of the original Arduino design.
Ive also talked about the intent of low power applications... it seems inefficient to me to have a v-reg on-board and hook up a 9v source just to turn that into heat for no good reason. I think its easy enough just to hook up a 5 volt source when not using USB or just use this on battery power. And if youre using battery you should have access to Aref just to make sure analog readings are on the up and up.
The extra analog pins are precisely that... extra. For the few times someone might need them they can easily hook up pin headers of one form or another. I did not want a situation where a user might accidentally hook up the two extra analog pins to pin A0 by plugging it into a breadboard. Ill put together a tutorial at some point showing a few ways of using those extra ADCs.
The Pico has been in development for over 14 months so its pretty cool to see it out there now. Thanks for the comments and keep them coming!
Brian
Edit: Mike I also noticed you have a non-commercial clause on your om328p... this goes against the Arduino Creative Commons Attribution-Share Alike license. You should reconsider as this seems to be in violation of making derivative works based on the Arduino design.