Have been crusing in and out of Baltic and Kattegat for last 4 years. One of the best places to cruise.
Lovely archipelagoes both W Sweden (Bohuslan) and Stockholm, Finland and Aland. Something like 60,000 islands in all (and about twice that number of navigation marks).
We did a 5 capitals cruise one May and June and had glorious weather throughout.
Lots of nice natural harbours, lovely people, good prices and all the services you need (mostly cheaper than UK). And no tide.
PM me if you want to talk and I will give you my number.