Just a quick impression. I've just recently caved in to K3. I'm still planning to keep the K30 as back up and my K-x because it isn't worth that much anyway in the used market.
Among my glasses, I've always found the FA43 a difficult lens with both the K30 and the K-x with at times inconsistent focusing under artificial lighting. With the K3, I was surprised that it focuses much (much and obviously) faster, and I find that the focus now hits EXACTLY where I want it to hit even under difficult interior lighting. With the FA43 now more tamed, and a significantly faster focusing DFA 100mm on K3, the K3 upgrade is a dream, and I'm now contemplating on permanently welding the FA43 with the K3
[My only complaint is button placements as I find the AF, and the AF select button too inconvenient and awkward as of now.]