After 6 days here's my battery usage. Which I have been tracking as it seems this is one of the area's the IPT is pretty weak in...All are with full charge...And some standby is included to account for "turining down volume etc" Most of these were done several times - minimum of 3 over the past 6 days.
EDIT: This is using it from"standby" and not turning the IPT on and off. Truning the IPT on and off drains the battery and provides unreliable battery usage tests as there seems to be no rhyme or reason for how much battery power is left/used in the on/off process.
Safari Only - max life just browsing internet has been 2 hours 40 minutes - 10 minutes of standby - total time just under 3 hours.
Safari - listening to music - max life 2 hours 5 minutes - ~ 20 minutes standby - total time just under 2 hours 30 minutes.
Youtube Only - browsing/searching on you tube and listnening/watching youtube video - max life 1 hour 50 minutes - ~ 5 minutes standby - total time just under 2 hours.
Video only(wifi off) - watching movies/tv shows - mixture of handbrake encoded and itunes tv shows - max life 4 hours 30 minutes - ~ 45 minutes standby. Total time 5 hours 15 minutes.
Music only(wifi off - and screen off) - let run with headphones in - volume around 65% - 8 hours - no standby - run until dead. Ran this twice - no other usage - 1st pass 7 hours 55 minutes, 2nd pass 8 hours 10 minutes. WOuld average total max time to be 8 hours.
Mixed usage - video/music - (wifi off) - browsing among library, picking tunes etc - about 50/50 between video and music - 5 hours 35 minutes and 30 minutes standby. Total time just at 6 hours.
Mixed usage with wifi on - but not used - same conditions as above - 3 hours 50 minutes, ~ 40 minutes standby. Total time 4 hours 30 minutes.
Mixed usage - youtube, tunes store, safari, video, music - aproximately 45 minutes of each, 3 hours 40 minutes, 20 minutes standby. Total time 4 hours.
Real life usage - not measured - mixed usage of youtube, video, music, safari, tunes store - Obviously what was used and for how long is unknown - aproximately 3 hours 30 minutes.
Average life of battery using mixed usage without measuring has been for me around 3 hours.
Average life of battery without wifi on has been about 5 hours.
This is in keeping with the specific tests I ran.
YMMV....