I used the Wiki before I got FO3 myself and rather used to tell my friend about quests, guns, etc., but now that I have FO3 I don't use it as much. I look at it without wanting to at first and then get svcked in. I'll try to go as long as possible without using it for Skyrim but I'll probably give in.

There are errors there from time to time but overall it's the best guide around - much better than the official guide, for example.

The first time I used the the Wiki was to figure out how to get to Oasis. I had the map marker from a random encounter but I couldn't figure out how to get around the rocks.

I use it mainly for background info, not to spoil quests unless I'm really lost as above.

I find the lore sections of the wiki to be very interesting - but the parts entirely about gameplay? Yeah, I know, I can play that. I don't need to read it.

I used the wiki to check if some unusual items I'm about to sell have some importance regarding quests or if some person I'm about to Contract Kill has something to do with a quest (marked or unmarked). I also checked the location of the Bobblehead of Energy Weapons. In the end, it felt so obvious then..