Alright, in an effort to prove a point I made an alt to go try and do Obsidian Sanctum fully prepared to document the many ganking horrors on the way there. :P
So, first of all, it's in a different portal/area of WvW than I thought it was, so I didn't encounter the anticipated hostiles on the way there. Made it to the JP entrance, didn't see anyone at first, then saw a group of 3 people, all with red names. ;_; Much to my surprise I get a party invite from one of them. O_o I say it's my first time in there and the leader says to just follow her. "Cool," I think. Things are peachy until we get just outside of the torch room, whereby the person kills me for no reason. Awesome. Not really the ganking I was expecting, but whatever.
Drop party, res at starting WP. Make it back to the torch room, all red names everywhere, in fact, haven't seen a single person from my server so far. Someone new offers a party invite, I figure I may as well cause they can just kill me if they want to anyway. :P This person turns out to be really cool and waits for me to finish the torch room (fell in there so many times to the flame spears I had to rebind dodge >_>), arena room non-issue, get to the top and she helps me finish the cache (even died fighting the group of Aetherblades, friendly fire FTL D: ) and tells me where to go for the magnificent chest.
So, have to say I was really surprised, especially after the many horror stories I'd read of other people trying to do it. The person from the other server who helped me said it was a good day. Outside of that first, semi-sadistic killing I didn't have any issues with anyone else.
Edit: Hah. So, just went to do it on my bf's account and now there's a group of about half a dozen people camping the well. Guess I got really lucky. Apparently they're camping everywhere, people are saying in map chat they've got choke holds and can't get through. -_- Oh lord, there is just a sea of red now all from the same guild stopping anyone from going anywhere. I'm sorry, how is this achievement not PvP related?