Arduino like verification

Because I am a software dude, I would like some help verifying this minimal Arduino based circuit which I designed with some changes.

It is single AAA cell operated (NiCd or Alkaline), needs to be very energy efficient.
Both ATMega and the DC Booster can be configured to any voltage between +1.8v to +5.5v, so I can go higher than +2.2v.
Input: 4 push buttons, each can wake it up from sleep using Pin Change Interrupt on port D (All switches are pulled up internally).
Once awake the circuit should read which switch woke it,
A visible light Phototransistor whose analog value can be read.
A tact switch whose on/off value can be read (pulled up internally).
Output is done by blinking an LED using PWM.
The software (including Arduino boot loader) needs to be burned over SPI using USBTinyISP.
The FTDI port is for Arduino IDE debugging.

Are there errors in the attached design? Anything missing? Anything can be improved?
**broken link removed**

I'm not conversant with atmel processors but as a general rule to save power.

Use internal pullups where available - tilt switch should pull low so you can turn the pullup off before sleeping.

Unused inputs should be tied low to stop oscillation.

If possible, switch to low frequency internal oscillator before sleeping.

Mike.

Mike
Very helpful.
So you suggest I just connect the switches to ground like this, and pull them up internally? (and turn off pull up for the tilt when sleeping).
Regarding unused inputs, isn't it enough to define them as tri-state to prevent oscillation?