I arrived in US on E-3 work visa Oct 12 and fail SPT for 2010 therefore need to file as NR. I am Single.

I have had $1,430 in fed taxes withheld for 2010. If I file 1040 NR EZ I will get $802 back in overpaid taxes.

If I were to file as a U.S. resident I would get $1700 or so back (including additional CA state taxes witheld) - unless I have made miscalculation on the software program I used...

Will I get the substantially higher tax refund if I file for extension and file as dual status when I meet SPT later this year?

If I do apply for dual status and when I file for extension, do I submit any tax information which would refund me the $802 I am owed as a NR for 2010 or would I have to wait until the dual status application was filed later in this year to get any of my refund?

In 99% of the cases, filing dual-status has NO significant effect on your tax situation, so it is likely better for you to file now rather than wait.