This is mine. Had it about 7 weeks. Not sure why you are worried about the weight of a TT bike, but it climbs just fine - just like a TT bike. I have ridden it around the front 3 gaps (north georgia mountains) once, and while I definitely scoot around the loop faster on my roadie, it climbs every bit as well as my P2. It gets over rollers just fine as well. It is no pig by any stretch of the imagination. I raced it for the first time this weekend and got around the course with one of the fastest splits of the day: 1150' of elevation over 17 miles, 22.9mph @ 3.6w/kg (NP) if that helps.
When we set it up at the LBS I was blown away by the overall micro-adjustability relative to the front end: you can move everything every whichaway without a whole bunch of complicated parts and bits. it is really, really smart. For me I wish the bar extensions were a little longer, and will probably eventually switch them out.
Brakes work great in both training and racing. Race this weekend was a little wet with lots of hot, 90+ degree downhill turns and I had no issues - never thought about them once, which I suppose is a testament to the fact that they work as you want them to. As good if not better than the ones on the P2.
The only thing that surprised me is actually how nimble the bike is - not sure why I was not expecting that. but it is solid as a rock and snappy. It had a lot of pops and pings the first time I road it (like any new bike might) but that all settled out and it is nice and quiet.
Only wrenching complaints thus far is the teeny-tiny 2mm (IIRC) allen screws that hold 4 fairings on (two over the front brake, one over the cables/wires in the stem, one over the rear brake). While I do generally like the design and how solidly they hold the fairings/cover on, the heads are so small they strip out just about every time you touch them. So, need to adjust your rear brake? strip out the screw heads when you remove the cover on the stem when you try and put it back in. Not fun on on the side of the road - next time I would just have left the cover off until I got back home with more than a multi-tool. You also have to take the front fairing off to charge the Di2 battery, so get ready to replace those as well on occasion. On the upside Felt obviously knows this is an issue and the bike ships with about a two years supply of replacement screws - they are all different lengths though, which is kind of a bummer as far as spare parts go. Make sure you get them from your LBS if you plan on doing your own wrenching. At some point I am sure I will be asking my LBS and/or SuperDave where I can get more of them. I don't think that is really all that big of a deal, I honestly think that is just the kind of thing you get in to with these so-called "super bikes."
Other complaint is with the wheel selection on the LTD, which was otherwise spec'd pretty much as I would have built up the bare frame. I had zero interested in the Mavix CXR80s, so I ditched them on eBay before everyone else that buys this bike does and drive the price down (hint - if you are actually interested in this wheel set, start scouring eBay!) I am sure SuperDave can outline all the great reasoning behind why the bike is spec'd with that particular wheel set, but in my case I already had a great set of fast tubulars and really wanted to make the switch to fast, bulletproof clinchers that I could ride every day as well as race, particularly in light of the PITA brake switching and adjustments due to the aforementioned fairings/covers/screws. Hence the Enves.
The last little complaint thus far is with the bento cover - like the idea of it and it is plenty roomy enough for a tube, co2+inflator, lever, small multitool, and a couple of gels, but you really have to cinch all that together. a couple of times during my race the gel I had stuck in there JIC kept bouncing the lid open. my solution was to just eat it. In training as you can see from the pic I just use a small saddle bag instead, as I always cary a couple of tubes, co2, patch kit, etc.
Again - none of the negatives above are big things to me - I absolutely am loving this bike and you will too, and could write pages on all the good stuff - but you can already read that everywhere else on the internets. These are just a handful of issues that I have found in the month-and-half with mine.
I'll do my best to answer any other questions you have.