Reasons
Jobs stated that Apple's primary motivation for the transition was their disappointment with the progress of IBM's development of PowerPC technology, and their greater faith in Intel to meet Apple's needs. In particular, he cited the performance per watt (that is, the speed per unit of electrical power) projections in the roadmap provided by Intel. This is an especially important consideration in laptop design affecting hours of use per battery charge.
In June 2003, Jobs had introduced Macs based on the PowerPC G5 processor and promised that within a year the clock speed of the part would be up to 3 GHz. Two years later, 3 GHz G5s were still not available, and rumors continued that IBM's low yields on the POWER4-derived chip were to blame. Further, the heat produced by the chip proved an obstacle to deploying it in a laptop computer, which had become the fastest growing segment of the personal computer industry.
Some observers were surprised that Apple had not made a deal with AMD, which has in recent years become a strong competitor to Intel, sometimes introducing technologies more quickly than the traditional industry leader. AMD's shorter track record and smaller production capacity, and Intel's significant brand awareness among the consumers and ability to also provide Apple with complete motherboard designs, have been offered as possible reasons for the choice of Intel.
. Apple switched their hardware and software to Intel 3 years ago. i dont think they will be going back to Power PC as its a waste of time and money. 
