MystOnline

• It is very very pretty.  Myst pretty, but in true 3d.  Eats grpahics cards for breakfast.  But you knew that from the demo.  It stays very pretty and has a large number of beautiful worlds.
  
• It is very hard.  Or I just suck at myst.  Actually, it's probably both.  I've got two puzzles cracked, I've discovered a third puzzle and have no idea what it's asking me to do, even.  Yay!  I've now completed two ages.  It's still hard - but it's not undefeatable.  It is buggy though - I had to reinstall to get one of the puzzles to work...
  
• The sweetspot for clicking on things is very small.  Presumably to stop you just swinging your mouse across the screen to discover what is clickable.  But it makes it hard.
  
• Unlike most of myst, a lot of the puzzles are time sensitive.  And there are jumping puzzles.
  
• Like most of myst, there's no death, nothing you can't undo.  Thankfully.  (Sometimes you have to reset the whole age though)
  
• Loading times are awful.  Really - five minutes to load a new age.
  
• Online play is laggy.  They accidentally approved every application, all at once - when they had intended to let people trickle in.  The servers responded as can be expected.
  
• SpoilerWarning.  You have to link out and back in to the start of an age quite often in order to progress.