After posting my last entry, I thought I'd elaborate on the G1's power usage. There's a useful little tool available on the Android Market called Watts, which logs the battery level and shows a graph of it. The image below is two screenshots from Watts.
The one on the left is the device's power usage last night, when I wasn't using the phone at all since I was asleep, but the phone was still checking my email and twitter regularly.
The one on the right was this afternoon, when I was watching the rugby at my parents', but also using my G1 a far amount for twittering, checking emails, texting, and looking up things like the words of 'God Save the Queen' and what a drop goal is.
As you can see, the standby life is pretty good, and you can probably get a good eight hours of reasonably intensive use out of the battery. Which is pretty poor, but I can live with it, since I don't usually use the phone that intensively.