Aphisit gets his chance.
Before we address any concerns, let's get something straight: Aphisit is the best choice for Thai PM. The alternatives are the father of Duang, a guy who makes even your average politician look honest, or a guy who messed up twice before. (The last choice is an interesting aside: why do so many Thais seem fixate on politicians who were utterly useless in their prime, let alone declining years?)
Aphisit is progressive, clean, focused and confident. Yet despite that confidence, people still ask questions about his potential to steer the ship in a storm. That's a pretty big criticism because let's face it - Thailand is in a political whirlpool right now.
Questions also hang over his independence from the PAD and resistance to influence from senior statesmen. Moreover, it looks as if we have arrived at the right answer for the wrong reasons. Aphisit is not here because he was the popular choice, he was here because the judicial coup left the door open for him. The defectors who changed sides did so only because they knew that sticking with PPP/Phua Thai would just result in another court case.
So I wholeheartedly wish "Mark" the best of luck. He's a good guy and the right man for the job, but he has a lot of doubters to convince and he needs to prove his mettle.
I'd liken Aphisit's position to a football manager taking over a team at the bottom of the table with a few games left. He needs to turn things around and fast but the pressure is on. The odd good result is not enough, the country needs a long streak of victories to restore confidence. It won't be easy.