What follows is the generic opinion of someone who isn't playing a druid right now.
Spirit is very useful if you need more mana. It's basically useless if you don't find yourself needing more mana. If you are going OOM in fights, and it's causing problems, you should get more spirit. If you aren't having any problems with mana you shouldn't.
By in large the posters at EJ are in the very best gear, and because of that they have no need for additional mana regen. There is likely more of it on their gear than they could ever want; hence they won't value it highly. This is typical as an expansion progresses, spirit gets valued less and less because of the way stats scale and the way mana regen interacts with the important metric 'time to OOM.'
In short it's something only you can answer for yourself.
As for a less vague answer, I've heard ~2,000 as point where you should have enough spirit to heal a generic raid encounter, but your mileage may vary. You can also plug your toon into treecalcs (a nice spreadsheet from EJ which I'm assuming they're still updating) and determine your time to OOM, which should give you an idea of whether or not you have enough regen to complete a fight. Usually once your 'time to OOM' is in the range of 7-8 minutes you'll have enough mana regen to complete about anything you come across (your mana will probably last a decent amount longer than the spreadsheet indicates as there's lag and occasional downtime in real encounters).
Edited, Dec 16th 2011 9:09pm by someproteinguy
That monster in the mirror, he just might be you. -Grover