Ever since my copy of Lightroom updated from 4.3 to 4.4 I've had TERRIBLE trouble importing RAW files. After pressing "IMPORT" the program will hang (showing as "Not Responding" in the Window Top-bar and in Task Manager) for 90 minutes or more. This is to import just 4 or 5 files.
I'm running on: Intel Core I5-2500k, 3.30Ghz, 16GB RAM, Windows 7 Home Premium 64 Bit
I never had this trouble with 4.3 and no other features of my set-up have changed except my Lightroom version.