It's definitely taking up a lot of juice when powering on.
The power management has not kicked in yet, the screen brightness is at its maximum the CPU probably is running at its maximum speed due to a lot of data being processed and daemons being run, it has to check all the peripherals before putting them into sleep mode or deactivating them, so ALL of them are for sure active and draining power from the battery.
The GPS chip is on initializing itself, the Bluetooth and WiFi chip too and, later, probably they are going go to look for available connections.
The flash memory is being read as the system and daemons and so on (applets, interface, libraries, you name it) load into RAM.
The card needs to be checked and the crawler needs to go look if there are new media files on it...

This alone it's a lot of stuff and almost everything is done at more or less the same time (those seconds it takes to load).

I usually bring it with me in the lab and leave it idle most of the time connected to the WiFi (I could say 95% of the time it's there sleeping and warning me of new IMs or mails, that's it) and at the end of the day the battery indicator is still full.
I use it the evening pretty much to browse the web and chat and reply to some mails every now and then while watching TV or spending some time with my girlfriend.
It usually goes to sleep with me with the battery indicator still full (but I know it's kind of lying to me).
If i let it run (may be I put it in offline mode), the next morning is still full or one bar (only one bar) has gone.
Today is such a day, it's 12pm (time for lunch!) and the battery indicator is half way telling me I have 1 hour of usage and 3 days of idle!
But, sometimes (very rarely and mainly because of modest being stuck trying to download mails) I turn it off the evening and on the morning.. those days it ALWAYS tells me I need to charge the battery.
Always.

And, to be complete, this are my settings: default ones. Brightness settings have never been touched, I've activated the blue led to tell me if it's on or not (that adds to battery drain), Bluetooth is alway on, but not visible (no icon for me) and WiFi is always connected (either in the lab or at home) and during lunch I move to another lab where it automatically switches to that WiFi AP while during the day I go to get some coffee two or three times and there's no WiFi down there (that all adds up to battery drain).

Overall I am VERY impressed on how it behaves when it comes to power management. Very. It's awesome.