I've got back from a quick trip to the seaside. My thoughts:

ibis Gdańsk Stare Miasto
I quite liked this ibis and its location (near the main railway station and within walking distance to the Old Town).
It's a new generation of ibises, with some local elements in decor. It looks nice. I was given a room at the very end of the corridor (a long walk), but slightly bigger than a standard room. There were a small desk and a small sofa/sofa bed(?).
In the room I found an electric kettle with tea/coffee, which was a nice surprise as ibis hotels in Poland don't normally have kettles. There were also two bottles of water and two small boxes of peanuts.
The breakfast was quite good (for an ibis standard), especially as in winter you can often get it for 1 PLN per person.
Longish queues at the reception desk around midday. Late check-out offered till 5 p.m.
I'd be happy to return.

Mercure Gdynia Centrum
It's a hotel that has been rebranded as Mercure recently. You can see some old elements (e.g. doors), but a lot of things have been replaced.
I booked a standard room but luckily I was upgraded to a privilege room on the 9th floor with a great view of the coast. It was a nice gesture as the hotel was fully booked on the first night (no availability through any of the channels).
VIP treatment: In the room, I found a fruit smoothie in a plastic bottle (Mercure brand). I stayed there just before my birthday, so there was a bottle of Mercure wine (white semidry from Moldavia) with a handwritten card. Welcome drink offered at check-in. We had a beer and a glass of wine at Winestone restaurant, which is in the middle of the lobby. Somewhat odd position.

The room was good size, with a comfortable armchair and a huge desk. The bathroom was new, with a shower (easily flooding the floor). The weak points: bed mattress and pillows. They need to be replaced in my opinion.
The room had both central heating and air conditioning. I believe it can get very hot in the room. We had a window open most of the time even despite very low temperatures in Gdynia (below zero).

Breakfast can be served in different rooms on the ground floor, depending on other events held at the hotel. The breakfast room was very busy on the first morning (since the hotel was full the night before) and much quiter on the second night. Good variety of choices, thought the quality of the sweet section could be improved (too many dry cakes). It's a pity they don't have a quiter corner for Gold/Platinum guests.

I'd probably return, preferrably in lower season just to make sure I get a room upgrade and that it's not too hot in the room.