We had to use this car for over a month because of an accident. We had hoped to enjoy it, as we have limited experience with Mercedes-Benz.
We found the GLA-250 very underpowered and hard to see out of, with unintuitive controls. It looks cool (at the expense of outward visibility), and I will say the seats were comfy. But we couldn't wait to get back to our X1.
Specifically: The transmission selection was like nothing I've ever seen. Seat controls are on the door. Wipers? God only knows. I couldn't find them. I also didn't like the inability to shut the rear hatch quickly by hand.
But the most frustrating thing was the lack of power. We were really surprised by how weak the engine was, especially with the provided transmission, which felt like my request for more speed was routed through Windows Vista. When you put your foot in the gas, there's a noticeable delay. Either there's too little low-end torque, or the electronic throttle programming is hinky, or the transmission is badly designed. Or maybe all of the above. I've had 4-cylinder, non-turbo RWD Volvos that were much more responsive (despite having less HP).
Making that worse, we could find no way to disable the distracting "shut off at every stoplight" eco-mode till further notice; you have to do it every time you restart the engine. In the X1, you can leave it off forever!
I actually tried the paddle shifters on the steering wheel. Even they were flawed. The car would not let me keep it in a higher-revving gear for engine braking or to keep torque high going up a steep hill (contrast that with the BMW X1, which intervenes only when you come to a stop, by putting the car in 1st gear if you failed to downshift). The M-B seems to assume you've never driven a stick shift and have no idea what you're doing.
Finally, rear and side visibility are very, very bad, due to the exterior design. Yes, there's a rear camera, but the view is not 100% (on any of them), so it's not safe to rely on those. And to change lanes, I had to crane my neck a la Linda Blair in The Exorcist just to check my blind spot. Even then, the C-pillar is so wide you still can't see for certain that there isn't someone in that lane.
Handling wasn't terrible. Ride quality was OK. The seats were great. But I would never buy one of these cars, at any price.