Thanks divnamite,
I personally think that the basic principles of both ETS offered GMAT and Perason Offered GMAT are the same.
However I am sure of this fact also. GMAC has certainly increased the level of difficulty in the quant section. You can see this clearly from the recent report of scores. The number of 51s in Quant has decreased drastically.
Here is what I think the GMAT administered by pearson VUE does. Once you get the first 5 math questions right it spits out 5 to 6 DS questions in increasing order of difficulty involving complex inequalities and number poperties. Most people are bound to make a mistake in one of these.
If you cross this sucessfully you will hit the Q49,50,51 level.
The first few questions in the OG are sitters. I found the last few questions to be alright. Your best resource is the forum and GMAT PREP. The quant section in GMAT Prep is very representative of the actual quant.
Vebal section has not changed very much.
Hope this helps.