Sometimes it's good to start fresh.. also, if you have good unit tests for your utilities then "testing" should be easy.. if you don't, then are they really well tested?
In theory, very true. In practice, it's an uneasy feeling of switching to a new tool, no matter what it is. Unit tests exist and are useful, but I still haven't mastered writing bug-free code despite all the testing
Every time I've had to use/touch MySQL, it has been extremely frustrating, and far more so than any other DB I've worked with (Firebird, Oracle, MS-SQL, DB2, SQLite, etc), with the exception of SQLite they've all been far more capable as well.
I don't doubt that's the case, but as usual with these things - you probably use MySQL the least and are least comfortable with it. In the last 5-6 years, I only ever deployed significant projects on top of MySQL or PostgreSQL, and while PGSQL was always more capable (and I personally enjoyed using it much more), it's not like MySQL is crippled - it is a decent tool which gets the job done.
My point is: PostgreSQL is exciting and nice and loveable, but MySQL is here to stay - web developers will keep it alive for years to come. We use much worse tools everyday, don't we?