The thing with merino is it's hot. Very hot. And I think I just tested the in the max possible temperature you could comfortably run. 21°C and it is hot out there. Merino wool may wick away sweat, but only certain amount can be taken care of before you are running in what feels like a wet sponge.
That being said, this is the winter item of clothing and we still very much in our “summer”. Being merino is very nice against the skin and is the choice of many sport brands base layer material. It's a nice general fit but not a slim fitted medium. So where this top may be fitted for most people, not being slim cut, It won't show off your athletic shape if you are a typically trim runner.
There are so many qualities of Merino and so many reasons why you should consider wearing merino items of clothing. It has great heat exchange, wicks away sweat, it is sustainable. And it really does feel great against your skin. More to the point, it is nice and warm. Some runners in the UK will wear short sleeves right up until ice comes. Maybe you are okay with just a longsleeved t-shirt on. But this merino top is definitely going to keep you snug it as a base layer or an outer layer.
We have taken this top outfit several rounds now and is extremely comfortable. Even though it is not technically cold enough to be wearing such a warm player of clothing, I haven't felt as hot running in this top as I do in some thick t-shirts. The zip however, does seem more like a fashion accessory than something functional for running. It is not low enough if it really is for ventilation and it does flap about. But zipped up I have no problems with it.