One of the things that they are charged with is making districts more competitive. In California, in 2002, 2004, and 2006, no senate or assembly districts changed parties, and 99% of incumbents have won this decade. State Senators and Assemblymen have gerrymandered their districts to make sure that their re-election is ensured, and when they are term-limited, they get to pick their replacement. The idea that communities should be represented by the same person, or that minority political opinions should have a voice haven't even been considerations. This has destroyed any accountability legislators should have had to their constituents.
Now with Prop. 11, a panel will draw the lines every decade, with the following considerations (from the San Francisco Chronicle):
Prop. 11 passed 50.6% to 49.4%, with support by many interest groups and the Governator (and oddly, Michael Bloomberg), despite strong opposition by Nancy Pelosi and the state Democratic Party. Although it's unlikely that California will elect a lot more Republicans in the next few years, it will create more legislative turnover, and accountability. Texas and other states would do well to follow California's lead in enacting similar measures and make the democratic process distinctly more democratic. A healthy turnover in power tends to restrain politicians and preserve liberty.
Commission members would not be allowed to consider incumbent residences or impact on political parties when drawing the lines. Instead, they would be required to follow these criteria, in this order: Adherence with the U.S. Constitution, including equal population requirements; compliance with the Voting Rights Act, to protect the interest of minority voters; geographic contiguity of districts; respect for the need to keep cities, counties and "communities of interest" in the same district; compactness of districts; "nesting" of districts so that the 80 Assembly districts are aligned with the 40 Senate districts to the extent possible.