What do I think of Planechase? I think it's pretty cool. It can create some really interesting swingy situations that completely turn tables in favour of a player that's doing really bad. Here are my top 3 and bottom 3 planes. Why? Because.
Top #3: Furnace Layer
One of the few things that New Phyrexia produced, I really like this plane. It's truly random since it can hit you too and players might be tempted to gamble and keep it around in order to hurt their opponent's but it could just as easily bite them for their hubris. You know, like an actual plane would do.
Bottom #3: Mount Keralia
Talk about a plane that you don't want to leave. While not the worst example of this (see #1), I still don't like this plane at all. Why would a plane hurt you for leaving it? I'll admit most of my dislike of this comes from my inner Vorthos coming through, but it just doesn't make much sense. A maybe boardwipe with a 16.6% chance of happening just seems terrible.
Top #2: Takenuma
This plane just seems so combo-happy that I love it. I can just see a scenario where a player loses the game when their Laboratory Maniac bounces when they roll chaos. It just really like it.
Bottom #2: Lethe Lake
Unlike the other two bottom planes, this is a plane that everyone desperately wants to get away from. Losing a sixth of your deck every turn just sucks and only having a one-in-six chance of getting away from it makes it even worse. It's like a blue player purposefully not ending the game so that he can toy with his opponent for multiple turns.
Top #1: Glimmervoid Basin
There's nothing about this plane I don't like. I love anything that can cause issues with control decks and this really does that well. Every direct damage spell becomes suicidal and every bounce spell becomes a boardwipe. It's just amazing.
Bottom #1: Sanctum of Serra
Usually when this plane comes out, we put the planar die away since no one wants to leave. There may be the situation where one player may want to try an planeswalk just so that they have a chance, but that player usually doesn't have the mana to roll the die more than thrice, so there's not much point in trying. And since when was the price of leaving Serra's house become burning everything you own?