Thank you all very much for your rapid and helpful replies!
I'm relieved to hear that the Kobo does not mess up ePub books. That was my main concern, since I will use it mostly to read books borrowed from libraries. The question was raised in an otherwise very positive review in this excellent French-language blog dedicated to e-readers:
http://aldus2006.typepad.fr/mon_weblog/kobo/
The reference to Calibre was just a minor point and need not bother you any further if the Kobo machine handles ePub books well.
At this point in time I think I will buy the Kobo rather than the Tolino. On the German Amazon site the user reviews of the Tolino are rather mixed - 6 out of 23 users are dissatisfied, whereas on the website of FNAC, the distributor of the Kobo in France, the user reviews are very positive - out of 455 users only 15 give it 1 or 2 stars.
One other point: dictionaries. I notice that the Kobo manual warns that the dictionaries may not function with books borrowed from libraries. Have any of you any experience in this regards? Perhaps I should start a new thread in a different section?
Thanks again for your help!