I just left Incheon 2 hours ago (greetings from Osaka JAL lounge); the terminal is definitely something to behold, but a couple of complaints:
- not all immigration areas are open at all times
- AA check-in not always at AA counter (JAL code-shares at the other end of the terminal
- JAL lounge is horrible
Other than that, nice terminal, short gate walks, ample if usual suspects duty-free, including great but expensive wine selection by gate 29, access is relatively easy, was 1 hour from Hyatt to check-in