I've never had a war with the elves, and have only once had to deal with their wood dictation, mostly because I use very little wood, buying metal from the trade caravans in exchange for their carting off the stones I won't need in the form of worthless crafts.
They can be a vital resource or a major obstacle, depending on where you are, and what you're doing. Metal industries not powered by magma traditionally had to use wood. At this point, elves are still useful since they tend to bring plenty of logs, so you can take 1-200 plus logs down in summer when they leave and have them all used up (typical for me, my wood piles are always empty.) That way there are no logs in your stockpile. They aren't currently smart enough to figure out that you cut anything down without you having a huge stockpile of wood.
They're most hate-able simply because I completely disagree with the way they want my dwarves to live, hate their attitudes, and I often accidentally offer them some wood product and they abandon ship almost immediately. At this point they get locked in and washed into the 'grinder', a waterfall on one wall of the trade depot that washes everything in the depot into a massive pit on the other end, where they promptly explode in beautiful gore, all on top of weapon traps to chop up any survivors. If i decide I really don't like them or the useless junk they brought me, I may well pour magma on it, but in 2010 I can just use the vast amounts of alcohol they bring to satiate my dwarves until the next elven caravan comes by, so that is often not wise.
So I am sadistic and often kill the elves, but I just as often ignore their presence/trade for petty things WAR BEARS.
On my next tundra map I may well start a war since their caged animals always die and I can get wood in the caverns.