With some BIOS versions the eee can drive a 1920x1200 monitor, but it seems it can't do decent power management at the same time! The table below lists those bios versions I've tested.
BIOS Version | 1920x1200 Support | Working ACPI |
8804 | Yes | No |
0703 | No | Yes |
0910 | No | Yes |
1001 | No | Yes |
1302 | No | Yes |