I haven't tried the Bianchi but own the Cervelo. I just want to confirm what was already said. The Soloist team (i.e. alu frame) is very hard. In fact, this is why I like it - guess it is personal taste. I also agree that fit is the most important. I tested more than 15 bikes before settling on the soloist. And, contrary to what several others mentioned, this is the frame that fits me fantastically (I'm 180cm, 63kg). I really didn't get along with the more sloping geometry bikes.
The soloist climbs OK (by climb I mean long 5-10% alpine climbs), though I've ridden bikes that were better for climbing. However, the solist decends like a motorbike - dead steady even at 80-90kmh. As someone else mentioned, it is not the best accellerator either, but where I really like it is powering on the flat. Being a relatively light rider I always had the tendency of being slowed by wind gusts, but on this bike I seem to keep momentum and carve through the wind. (Being a physicist, I realise that a frame can't make that much difference, but I'm reporting my perception. And in riding, perception feeds back to performance).
Incidentially, I occationally ride it with a aerobar (the lightning stryke from profile design with matching lava stem). It is not a tt-bike but comes pretty close.
I believe that the 'weakest/cheapest' part of a bike determines its quality. Hence, in my mind it makes little sense to get top-of-the-line frame with medio group, conversely would also make no sense to get dura ace with a cheap frame. In that respect, there has always been fancy looking frames (remember those humongously oversized alu-tubes) mounted with mediocre components to lure the eye of buyers. The soloist is a good (albeit somewhat heavy) frame with a good component group, and that at a reasonable price.
Concerning what the professionals ride, remember that they have a different budget, mechanics support etc. What is best solution for them is likely not best solution for many of us. for instance, most of them ride tubulars, but that doesn't mean we have to. Btw. if I remember correctly, jens voigt and several other csc riders raced and won on the alu frame just few years back.
ATB
Henrik