No time today for game analysis, at least right now, so I'll just report the results and my superficial impressions for now and leave it at that. [UPDATE: I've since annotated the games - see link at the bottom.]
Nakamura briefly had Kramnik on the ropes, but it was a crazy position and Kramnik escaped. Gelfand - Grischuk was also crazy, and judging by Grischuk's body language at the end he must have felt that he had Gelfand at one point.
Mamedyarov - Aronian was less wild and at least superficially didn't seem to have one player or the other miss any big chances. That game ended relatively quickly, unlike Karjakin - Shirov and Wang Hao - Eljanov. In both cases Black (the two 0-3 players) had to suffer a long time before scraping out their half points.
Standings After Round 4:
1. Aronian 3
2-6. Karjakin, Wang Hao, Mamedyarov, Nakamura, Grischuk 2.5
7. Kramnik 2
8. Gelfand 1.5
9-10. Shirov, Eljanov .5
Round 5 Pairings (on Wednesday; tomorrow is a rest day):
Shirov - Nakamura
Aronian - Karjakin
Grischuk - Mamedyarov
Eljanov - Gelfand
Kramnik - Wang Hao