If an employee changes jobs, he or she automatically loses eligibility. See the FAQ on changing jobs during and after immigrant processing for more information. As with all other immigration petitions, unless you are qualified there is no chance of approval. If a beneficiary is qualified, then the probability of success depends largely on the way the case is presented. If the evidence is relevant and well presented, and the argument is made persuasively, then the case should be approved routinely.
Most petitioners confuse quantity with quality.
As a result, they substitute hundreds of pages of supporting documents for a few well crafted supporting exhibits. INS examiners have a limited amount of time to review each petition. If they run out of time while going through an excessively lengthy petition, they will not take time away from other petitions. Rather, they will just stop and make a decision based on what they have seen up to that point. Second, the letter must clearly explain how the letter writer came to know the factual information stated in the letter.