You're probably right, and battery life varies a bit day-to-day. I haven't done a formal test to double check my statements above, more just a feeling.
I've had the phone for a while and the battery has gone through many cycles. It has definitely lost some capacity.
The modem asserts a wake pin when you receive an SMS or phone call, causing the SoC to wake up. Services that rely on data (IM, e-mail etc.) don't wake the phone up (they will rely on periodic wakeups in the future, but there's no infrastructure for it yet).
An update that makes communication with the modem after resuming from system suspend reliable has been deployed today (previously it would often fully reenumerate and cause various troubles in the process, now it's instant).
It didn't jump up suddenly; there were many software improvements in regard to battery life deployed through the years which together sum up to a pretty significant change.
There's not much difference in battery usage between hardware batches, the improvements were mostly in software. The battery capacity has changed though - the earliest batches that some early backers opted to receive had a 2000mAh battery, while later ones had 3600mAh one. The mass produced version ended up with 4500mAh.
The early batches shipped with early software, and that was actually the biggest contributor to bad battery life and (now long solved) overheating issues.
Okay so some people don’t even have the latest hardware revision so they’re stuck with a phone that will never support suspending and will have terrible battery life forever?
I get about 3-4 hours of active usage (like Web browsing), about 8-12 hours of idle time and about 20-22 hours of suspended time. More with modem off, but then it's not exactly a phone:)
I'm honestly almost always near a charger, which I also realize is just a cope.