I have been with SquareSpace for a couple of years now and for the most part I have been really happy with them.
But lately I have been looking at WordPress and even set-up a test site to test it.
I like all the plugins available and themes options but I don’t know if ist the host (BlueHost) or WordPress but the editor part is slower than SquareSpace not a big deal but noticeable.
The main reason to consider WordPress is price. SquareSpace can be a bit expensive but is a really good platform to only consider price.
The other issue is moving from SS to WP I am concerned that I will lose pagerank and back-links plus all the manual work involved in making sure all post are formated correctly after the import. I guess thats the Catch 22 part.
SquareSpace has a big update coming soon as Version 6 is been beta tested. I haven’t try it but those who had said is a solid upgrade so I have decided to stay with SS until I have the chance to see whats new and better and then decide if is worth moving to WordPress.