For me, as a (power) user/developer with a decent understanding of what things on the device use how much power, I seem to get between 6-8 hours of heavy usage.

Higher than some because of tweaks rooted in knowledge of how the device uses power (lower backlight, push email, always 3g or always 2g depending on location/situation rather than dual mode)

Lower than some due to high usage and games.

I agree that Constant/Persistant data transfer (no matter how small) are the bane of the devices power source.

The device seems quite good about going into idle/low power states when possible (aside from the potential wifi bug discussed elsewhere on this forum)

But if you have things constantly transferring data, your power efficiency will suck. 3G, and the power saving behavior of the WiFi radio on the device are oriented towards burst traffic with periods of inactivity between (web browsing), not slow steady streams of data.

Yes, this is supported by my current findings with my battery drain tests. I wonder if it's possible to fine-tune the IM plugins to NOT check who is online constantly, but say every five minutes or so? Or does that go against the APIs from Skype/MSN/Google? It seems unnessesary for the IM accounts to constantly exchange information from the servers.

in that real life usage case i get sometimes 8 hrs and sometimes more than 15. i dont cut low on the most important things as internet and phone, sms and im (3g).
i wait with wifi till the drain-bug is fixed and this way i am satisfied its not great but satisfied. when im at home i charge it whether its half full or empty and when im out i sometimes have to think about my use in order to maintain being reachable. but thats usually due to lack of charging. getting a 2nd battery i will never. if i notice i cant cut it with the one battery i think im gonna get an other phone. that'd be ridiculous. its balancing on the edge but im sure it has to improve one way or the other in the future by software etc.

Getting about ~11 hours usage.
Charge overnight: wake up at 7:30am
browse for 15 min in bed.
MS Exchange Push kicks off from 8am until 9pm (push times, other times manual). Receive about 50 emails /day
I also have a GMAIL imap connection open all day. receive about 30 emails/day.
Spend maybe 20 minutes a day on voice calls. Send/receive about 25 texts. Additional ~1h of browsing. Play DrNokSnes for ~15 min.
by around 6pm the battery is nearly cooked in the red zone.

I have a feeling the MS Exchange and imap connections drain the battery. I get about the same results on both 3G only and 3G/Wifi

After installing openssh I think my battery life decreased. I wonder if there's something it's doing (it's running as a a server) that's draining it faster..

About 24 hours with regular usage:
1 hour ecoach activity
6-8 hours browser activity
8-10 msm out-in
2 phone out call
10 mins of video record
some photos
and some contacts editing

You can (as root) do:

to stop the sshd and see if that helps with battery life at all.
Note, if you reboot the phone sshd will automatically be enabled.

Not sure about skype, but on MSN, AIM (and I'm pretty sure Jabber/gTalk status updates are pushed by the server, not pulled by the client at intervals.

If a protocol has an option to suppress these messages that might potentially reduce power usage.

Unfortunately Skype is a completely closed box, protected by obfuscation layers and legal threats. You're 100% at the mercy of Skype and it's handlers for any improvement there.

I've successfully used the device on SIM most of the time and wi-fi whenever available, down to half charge after 2.5 days. However, I press off-line mode before going to bed.

I've turned off GPS and location services and vibration.

lowering WiFi from 100mw to 10mw gave me an additional 3-5 hours usage. Nothing else was done. Mail every 15 min x 2 accounts. MfE constant - between 8 and 22.