[quote author=Coding Badly link=topic=128048.msg963429#msg963429 date=1350685402]
Addendum: The start-up delay is also used to ensure the clock is stable. You will have to consult the datasheet [/quote]
If I read Table 8-12 on page 33 right, it looks like the SUT delays are not used when coming out of powersave on an internal RC oscillator; only a fixed 6 clock cycle delay is used when waking up. So it seems I'm not wasting any battery power by sleeping and using the 65ms SUT.
But, it's conceivable that if you try to Serial.print straight after coming out of powersave, you may confuse the receiving UART with excessive clock slew. If this is important to you may want to do some testing. In my own sketch I wake up, do a digitalRead, and then Serial.print with no problems so maybe digitalRead's slow performance is an asset here. 