I’ve been looking at upgrading one of my past clients from Doctrine 1 to Doctrine 2 and so far it’s looking from my end like a done deal.
I started here by paging through this ( http://www.slideshare.net/jwage/doctrine-2-not-the-same-old-php-orm ) slideshare on Doctrine 2 and before I got bored with paging through 94 slides I already had a warm fuzzy feeling.
My initial tests have shown that Doctrine 2 without a doubt needs support from APC or memcached, but with the exception my few and far between dumb/cheap client’s is almost guaranteed to be present. Otherwise I like the decidedly simpler syntax for defining domain models as simple classes without inheriting some super support class.
Last bit, my stackoverflow answers regarding doctrine 2 so far