Overall I enjoy the Titan series, but I find it a bit hit and miss. Overall I like the characters - the core characters are all quite engaging, but the "secondary" cast is a bit uneven.
I enjoyed Taking Wing, Orions Hounds, Sword of Damocles, Destiny...contrary to popular opinion (judging by the poll), I wasn't particularly engaged by Over a Torrent Sea, and I didn't really like Synthesis. I would have liked it more if its portrayal of technology had just made a bit more sense. Seize the Fire was just painful to read - the plot was fine, but the large number of unpronounceable (and unmemorable) names just made it feel like a struggle - and to be honest, if I'm struggling to read a book, I'm not enjoying it.
In general, I'd read more Titan, but I'd like some more from Mack, Bennett or Thorne, as I've kinda disengaged with Martin's style. He worked better when he was co-writing with Mangels.