Its more than adequate for the level of detail it is showing. If they were attempting to show results separately by Democrats and Republicans or by Norther CA vs. Southern CA, then it would be small. However for what is is, a quick statewide snapshot at the beginning of the campaign, its fine.
The statistical error for the given sample is +/- 4.3%, so its clear that Arnold beats all comers at this point. It also shows that simon has "at best" an 11 or 12% share of the electorate.