I have just spent a very pleasant 36 hours in Poznan, here are some of my thoughts.
Unfortunately the city centre is being renovated - Stary Rynek, the main square, is a complete mess: however, when all of the work is finished it will be lovely, but I would not bother with a visit this year.
I arrived late on Saturday: the only ATMs at the airport charged for withdrawal, but luckily the taxi - cost 42zl, 50 with tip - took a CC. ATMs are hard to find, I finally found a Santander ATM half an hour before I left, but most places take a CC.
After checking in I wandered the streets for an hour, then had a nice supper in Verandah, typical central Europe portions, main course was enough for 2 people, ice cream for dessert was first class, and good beer, no idea what it was called.
For breakfast on the Sunday I crossed the Warta to the suburb of Srodka, which has some nice street art, and had an excellent breakfast at the cafe DYN - recommended, good coffee and choice of music.
I wasn't able to join a free walking tour, but there is plenty to see without - I downloaded the itinerary of one of the walks and basically followed that. At 13:30 I made my way to the croissant 'museum' to watch the 1 hour interactive St Martin's croissant demonstration - informative and amusing, and a small croissant at the end: cost 33zl.
For supper I went to Bo, bit of a leg from my hotel but food was fine, even though I had to have the veggie option as they had run out of pork (!). Unfortunately it then began to rain hard (cheeky waiter said "this must feel like home") so I turned in for the night.
Monday morning I checked out early and made my way to Bo again as their breakfast was recommended by a local. I wasn't disappointed, and it had the advantage of being close to the Hotel Mercure, whose coffee shop is supposed to do the best St Martin's croissants in Poznan. Again not disappointed.
Would I go back ? yes, but would try to avoid Sunday as some places were shut.