I reached USA on 8th Aug 2010 (lived almost 145 days till 31 Dec 2010). I am on L1 visa and planning to be in USA for almost 3 years. My wife and 2 kids are on L2. Me and wife are having SSN. This is our first visit to USA (means, were not present in 2009 or 2008 for calculating SPT). I am from India, working at CT (client location) and my employer is in NJ.

Having said this, what is my status for taxation as of 31 Dec 2010? Should I be filing 1040NR as a Nonresident alien? This is the direction I got from 2 CPAs and I filed as per that through one of them.

I have a friend having the same status as of me (L1, landed in USA on 8th Aug 2010 for the first time, same employer, client etc) contacted a 3rd CPA and they claimed that he is a Resident alien for the purpose of tax filing. They went forward and e-filed his return.

I would like to know which approach was correct.

Another question is, will I be able to amend this NR filing once I complete 183 days in 2011 through first year choice?

You are a non-resident alien for 2010 and as such would file a 1040NR or 1040NR-EZ. And you are right, you can amend your return after you pass the SPT and use the first year choice. You would than be dual status aliens for 2010, but since you and you wife are resident aliens at the end of the year, you can choose to be treated as resident for the entire year. If you do that, you will have to report worldwide income for the entire year.

Thanks for your reply... Not sure if I understood you fully...

You said
"You would than be dual status aliens for 2010, but since you and you wife are resident aliens at the end of the year, you can choose to be treated as resident for the entire year. If you do that, you will have to report worldwide income for the entire year."

This is applicable only once I pass the SPT... correct? So by April 18th I SHOULD be filing 1040NR or NR-EZ. Sometime in June/ July once I complete 183 days in US I can amend it with resident status.

Sorry for asking too many questions. Can we apply for ITIN# for my kids when I file the amended 2010 return? Will I be able to claim the child credit at that time?

If you don't pass the SPT by April 18th, you can file for an extension and file your return once you pass it. Just pay any taxes due by April 18th, as the deadline is for filing, not for paying.
The IRS statutes say, that you cannot claim a non-resident alien as a dependent, and the first year choice only applies to the taxpayer and spouse. However, others say, that the child assumes the residency status of the parent. The best would be, if you take your return and the ITIN applications to a IRS taxpayer assistance center. They will tell you if you can claim them and process your ITIN application. You won't need notarized copies of the passports of your kids just the originals.