I haven't ridden a Guru tri bike, but a good friend of mine has one. He LOVES his bike! Rides like a dream and is really great. He loves it as much as I love my Cervelo (which is a whole lot). Can you test ride one before you buy it? Guru was on my list for a new tri bike, but it got beat out by the Cervelo. Just personal preference.
And I've heard nothing but good things about Jamis bikes. Top quality.