I've been with them for my main (only) bank account in Germany for three years, and can recommend them (and also have a number of colleagues at work who are happy with them). Only drawback that I can see is that they don't have that many branches (although they are nationwide) and that branch opening hours are laughable (literally not much more than a couple of hours a week in Rostock, may be different in bigger cities), but apart from paying in the odd refund cheque and a bit of account admin (which can generally be done by post/fax/phone/web, unless you need to present an Ausweis) then there's not really any need to go to the branch.
Money withdrawals on the EC card are only free on DKB ATMs, which seem to only be in their branches. Otherwise ATM withdrawals on the Visa card are free nation- and worldwide (even outside Euroland), and since any deposits in the Visa account attract a (for Germany) very good rate of interest (currently 3.8%) then I usually transfer as much as possible straight over to the Visa account and use that as a savings and instant cash account - if you need to transfer money back to the Giro account to cover bills, rent, etc. then you can now do so online since they upgraded their banking software last month. Using the Visa internationally in shops attracts an average commission, as does use of the EC as a Maestro internationally (get yourself a UK Nationwide current account and Visa to get those free from commission!).
I've no idea what their other charges are like since I've never paid any (or compared to other banks), but they're all listed on their website
, in case you haven't yet found them.