...reliability doesn't seem to be affected anymore than Ext3 for the typical use cases...
That sounds like a "weasel phrase". "Typical Use Cases"? The lofty goal of ext4 is now to preserve user data in "typical use cases"?
If I mount two filesystems, one ext3 and one ext4, both using the defaults. And then open a new file on both, write some data to both, close both, wait 30 seconds, and pull the power plug, what happens?
If the answer is "the same thing for both" or "ext4 is more reliable in that scenario" then great. If the answer is "ext4 is less reliable" then ext4 will never see my production systems, with or without nodelalloc.