The 3vo is not an Evo and it's best to leave preconceptions behind.
Battery Nirvana is oh - so enticing - but best to approach the 3vo as the leap of technology that the Evo was last year.
The SBC mod, controversial in its day, ought not be approached complacently for the 3vo.
With just over light use, I am getting 16+ hours out of about half the battery, no root tricks.
I have every confidence that those with less have more normal usage habits than I -- but primarily suffer from the known evils of bloatware.
I'll be suggesting to do first what we know as experienced Android rooters: remove bloatware, control nonsense net access for marginal apps with DroidWall, install Adfree and make only conservative config changes.
Approach device specific mods only after that and only after the device is treated as the new tech it is.
But - that's just my opinion.