I stay in Taipei fairly frequently, and with the drop to Cat 3, decided to try the new Courtyard.

The rooms are brand new, well appointed (although the furniture is a bit Ikea-ish), with very comfortable mattresses. The hotel only has 8 suites, so upgrades seem to be mostly of the "high floor" variety, especially for longer stays.

The club lounge is fine, with excellent staff. Good selection of liquors, although the food options are a little weird and repetitive. The outdoor area is lovely. Indoors, I wish there were more 2-top tables rather than the large shared ones (but I guess that came out of the millennial focus group that also brought us no work desks in the room?). I wasn't given the option of having breakfast at the restaurant.

I didn't like the location. There's no direct MRT access (unlike CY Nangang, W, Hyatt), and it takes a bit of a walk. I suspect most people staying here are on business and take taxis/Uber. There's not a lot of activity in the immediate vicinity at night, even though I grabbed some decent street food.

Marriott has some great hotels in Taipei (and the Hyatt is decent too), so there are a lot of strong options to choose from. Generally, the two Courtyards, Aloft and Sheraton will be in the 5000NTD range, while W/LM/Hyatt/Marriot are pricier. If paying cash and restricted to that lower range, I'd pick the Sheraton. If using points, the Courtyards are of course a much better deal. And if one has to choose between them, I think for tourists, the Nangang property is better -- higher chance of a suite upgrade, slightly better club lounge, easier public transportation. But the Courtyard DT is by no means a bad choice.