I think TinyLily is a fantastic board. However, for many applications there are really too few I/O pins. I understand, that there is no space for more sewtabs.
But it should be possible to add small solder pads for the remaining I/O lines on the back (just like the ISP pads).
Personally I do not like the current connector for serial programming. It takes a lot of space and requires solder pads on both sides of the board. I think that five flat large pads on the front side would be a better solution. You could use a small peg-style connector for programming the device.
With this small modification the TinyLily can be used for almost all Arduino applications!
