After a short acclimation period, it's got potential! The trolley car is awesome and super convenient, the roads and sidewalks are paved and mostly clean, there's a good amount of greenery, it's very walkable, there are less beggars than Poblado and doesn't seem dangerous. The biggest downside is all the buses driving on those roads and the black, disgusting smog that comes out of their pipes filling the air almost the entire day. The other downside is a total lack of nice cafe's or coworking spots. The best you'll get is instant coffee in a small plastic cup with tons of sugar.
My Airbnb in El Centro of Medellin was pretty nice. At about $40 per night with a 10% weekly discount. The owner only rents on Airbnb. There's a couple other nice spots. One is on Airbnb at something like $70 a night. That's way too high. You can find a very dope spot in Poblado for that price and it didn't seem any better than where I'm at currently, maybe a bit worse. This is also a nice look building with an epic rooftop and affordable prices including a little coworking space and a soon-to-be cafe on the ground floor. The downside is that the rooms are fucking tiny and even the larger ones were horribly put together.