Good summary. It would take a major last-minute scandal and weird second round participation dynamics for Matthei to be able to win.
Taking Bachelet for granted, the big question is whether Andre Velasco will be able and willing to bear the same no-nonsense influence he had during Bachelet's first government. If he does, he won't be able to counter Bachelet's ineptitude and passivity, but at least the damage will be contained. Otherwise say goodbye to sound budgets and a return to corruption at a scale last seen during Lagos' government. Bachelet's own instincts are far to the left, as is demonstrated by her choice to move from Australia to hardcore pro-Soviet Eastern Germany in the 70s! Ask yourself why the unapologetic Margot Honecker lives in Chile. Bachelet has the Communist party's support, unlike under the Concertacion.
Four left to hard-left former student agitators were handed parliament seats on a platter. There's going to be big pressure for free (otherwise known as ruinous) state-provided university in jobless tracks such as sociology so that young Chileans can pretend they're studying into their late 20s while staying with mum and dad. French-style overcrowded public universities disconnected from the workplace is precisely what Chile does not need. The right coalition wants education subsidies to be means-tested, which any sensible person will tell you is the right thing to do, but somehow free nonprofit education is a basic human right.
Chile's public finances are overly reliant on high copper prices so the conjunction of increased public spending - which would be by and large waste, see: Bachelet's Transantiago/earthquake complete lack of any executive ability whatsoever - and dropping copper prices could prove quite a brutal squeeze on the country. Already there's a current accounts deficit, as Chileans are unable to increase their productivity in line with their thirst for imported manufactured goods.
Posted from Central coastal Chile, where like in most of the country outside of Santiago and the northern mining region, GDP/capita/year is circa $10K and you can clearly see that becoming a developed country - with the expected human capital, environmental standards, cultural options and everything else people in rich countries take for granted - is far, far away.