So, just a little report on our stay in Turku. In a word, I was astonished at how ugly most of the city is, especially after flying in from gorgeously restored Gdansk. A few bits by the river have been prettied up, and the castle (quite a hike away on foot, btw!) is nice enough, but most of the city is just terrible, an endless row of 70s-era concrete monstrosities filled with kebab joints.
It also turned out that we'd arrived on Ruisrock weekend (one of the country's largest rock festivals) and hotels and such were packed. Finding a decent place to eat after 9 PM on a Sunday turned out to be a chore though, the "green card mafia" (S-card group) had the city center restaurants locked down solid and in the end it came down to a choice between Rosso and Hesburger.

Rosso had salmon soup and won, alas (just as bad as I expected), so next day we had to go for Hese -- their pork steak on rye bread burger with cucumber mayo ain't bad.
And oh, Turku Airport's T2 (LCC only) is pretty shocking, it's quite literally just a utility shed. Arriving there isn't too bad, just pick up your bags and go, but waiting for a delayed flight wouldn't be fun. The taxi stand consists of a lone pole in the middle of a parking lot without even a number to call, but fortunately we'd cribbed a Turku guide and could order up one -- and the ride to the city cost nearly 30e with Sunday and advance booking surcharge.

(There is a considerably cheaper bus, but we had a bit too much luggage for comfort and didn't want to wait around.)
In all, I'd have a pretty hard time recommending Turku for anything more than a short stopover on the way to/from the ferry.