I know, buy the bike that fits you.
I've narrowed down my search to the following three bikes:
Giant Trinity Composite
Cannondale Slice
Felt B16
The Cannondale or the Felt would be the safe bet, probably can't go wrong.
The Giant seems to hold a bit more "advanced" design, but I can't seem to find any good reviews. Anyone have any opinions on this one?

Are you looking at the new
Are you looking at the new Slice Force or last years Slice w/ultegra?
I test rode a Giant roady (can't recall the name) and the Cannondale Synapse and they were both excellent. I chose the Cannondale because I liked the fit better and the customer service as well. With that said, I do not see many Giant's on the road around me and there is a Giant dealer 1 mile away. I have been seeing more and more Cannondale and Specialized.
I also have the Slice Ultegra from last year and I absolutely love it. It is fast and so comfortable.
Any one of those bikes would be cool. Which one is calling your name?
The Giant calls my name
The Giant calls my name because I like riding brands that aren't as common. Loved my Kuota, wonb't ride Cervelo. I don't really dig the color scheme, one buddy loves it, and a "trusted advisor" isn't too fond of the bike.
I'm looking at the Cannodale Slice. It's the closest to my current geometry, and is certainly smooth as butter. Feel like a comfy ride, but not sure it's as stiff as I would like.
I feel like I'm gravitating towards the Felt B16. I love the fact that I can get a quality frame with Ultegra components in the low $2K range. It's a bit lower and longer than I'm generally used to, but I think it's probably where I'm leaning.
I haven't bought a tri bike in five years. It's funny, we all talk about "buying based on fit", but what I'm finding is that there are a really large number of bikes out there that fit well, or can be adjusted to fit well easily, unless you happen to be on the extremes. Being 6'1" with a 32" inseam, I'm pretty easy to fit.