The latest release of Gmail appeared in the Market today on my HTC EVO. With it came a few features that have been lacking, including the ability to always show pictures in email (per user) and to play custom sounds based on email coming in to various labels. Google also list unspecified performance gains, but it wasn't exactly slow to begin with so I'm not sure what they did there.
In terms of battery savings, Gmail now includes the option to only download and sync priority mail, which should cut down on some of the over-the-air traffic caused by your favorite email-forwarding friend.
There still isn't the option to always show pictures for everyone, play custom sounds by specific sender (you can work around this by labeling them), sync scheduling options, or filter out any emails containing LOLcats or pithy sayings, but it's another step in the right direction.
Grab it via update or download from the Market, as it seems once again to be worth it.