1. I really hate the map. 90% of the map is devoted to ocean and Russia, and the interesting bits are crammed into the remaining 10%. It's incredibly easy to misread the map and fuck up a move. Perhaps this is intentional, but it drives me nuts.
2. I didn't know any of the people, so I couldn't judge how honest or deceitful they were being. Maybe this would be better with friends whose tells I know better.
3. Sweet god, you're right, it takes forever - and yet you're feeling rushed the entire time, since you have to make sure you talk to at least the people you're nominally allied with for the next N turns, as well as hearing out potential new allies, and trying to make new ones of your own.
I guess I'm just too casual of a gamer for something like this, but if you think you're interested in playing Diplomacy, I very highly recommend that you try to find someone in your area to play with - there are probably six other people just like you wishing they had someone else to play with.
As for friendships, I think one has to state clearly at the beginning of the game that one has a strong chance to turn against their allies at some point. It's a feature of the game. There are ways to manage this risk for one's sanity. :)