I have the Italeri B-17 Fortress I kit and have started it. The thing most everyone will tell you is that the dihedral of the wings is exagerrated. I shimmed my upper wing halves at the fuselage joint and got the wings to almost level, which is what it should be I am told.
The landing gear mounting angle will need tweaking to compensate for the change in dihedral. I hate the way Academy engineered the gear mounting system, as you have to add them before gluing the wings halves together. The tires are weak on detail. True Details makes a replacement, but as all of their tires, look flat.
The nose cap has huge molded-in holes for the later B-17 guns, but Squadron makes a vac-form replacement with these holes closed off. The cockpit roof has a teardrop fairing that is thick, but the Squadron vac set has it already molded onto the roof. The other clear parts on the Squadron set are not really needed, as the kit parts are acceptable. The small rectangular windows around the nose need some sheet plastic shims in their openings to fit snugly.
Finally, the interior is highly suspect or missing altogether. I tweaked the kit's front office just a little. The instrument panel decal is a joke and looks terrible - but I used it anyway! I scratchbuilt the missing sections of the rear crew compartment. You can't see much except for maybe the radio operator's section via the dorsal window. I painted the aft fuselage interior green, but later found out that it should be aluminum.
Hope that helps, not hinders your build!