This might sound crazy but it's pretty likely that you can find a ride back to Seattle from the festival just from the people you meet (assuming you have a way there, how does that work?)
My group has given a few people rides back to Seattle or Bellingham because their friends were leaving earlier then they wanted to leave. Almost everyone is going to be going through Seattle on their way home. Many have an extra couple seats.
That being said locking down a ride before hand is always a smart idea.
There's these things called planes, they get people places pretty quick.
Best bet, fly to Seattle on Thursday (earlier the better) and see if you can find a ride with someone or rent a car if you can afford it. Or just wait of Osheaga because I bet the line-ups will have lots of overlap.
Some of the major ones have changed, but last year I experienced two of the best festival crowds I have ever seen (Tall Tree and Pemberton) so there are still good people out there, they have just moved on. I'm pretty sure the change in crowds has more to do with the fact we are all getting older rather than the crowds actually changing.
Oh and side note Coachella was awesome last year and the year before. Sure there are terrible people that attend but I found many a group of awesome people all by myself at the right shows. If you refuse to do Coachella because of what you think it is you are missing out on one of the most impressive music festivals in the world in terms of line up (this year kind of blows though) production (some of the art is hands down amazing) and overall organization (there's 90,000 people there and it hardly feels crowded most of the time).
Well Passion Pit and Run the Jewels will crossover to Pemberton. Weezer maybe, which I'm cool with because I still maintain my opinion that they are a lot of fun live. Other than that Blondie and TVotR played Pemberton last year.
Pretty good line up but I preferred last year and I'll be doing Pemberton anyway.
If you've got premier camping getting in shouldn't take long. The last couple years they have lined everyone up into roughly 10 different lines (kind of like getting into Coachella camping) and any extra will line up down the road. Once you make it through the road line (if any exists) there is different way to go for Premier I believe. Basically you should be fine.
Traffic seems to be pretty hit or miss regardless of when you arrive. They do seem to have gotten a little better in the past couple years, but that might change with the charging for camping thing they now have.
Getting there earlier or later has zero impact on where you end up. It's a total crapshoot and often people who show up later end up closer to the venue. I'd recommend getting there well before the sun goes down thursday so you have a couple hours in line and still some daylight to set up.
I've also never heard any soundchecks from the mainstage in camping, so I'm not sure about that.
Given how bad it was last year they would have had to put out an amazing line up to even get me to consider it. I was never planning on going. Shambles is still a maybe, though more leaning to yes at this point.
That Squamish lineup is beyond terrible and I'm not going to miss much of that at Pemberton. There is a legitimate possibility that when they release the day by day lineup there will be days with nothing I would want to see, which is mind boggling for a festival that costs that much.