Calibre can be confusing because it is almost infinitely customizable, and the documentation leaves something to be desired. In its most basic form it's not really complicated.
I got a new laptop about a year and a half ago and when I copied over all my ten years worth of pdb, prc, and mslit ebooks that I had scattered around in various folders I realized they added up to over a thousand mostly unreadable books. It made me very determined to finally do something about them. I just stuck to the most basic parts of Calibre, and it really wasn't hard. The plugins actually have better documentation than Calibre itself and once you have them set up they just work automatically.
Another really good thing about having Calibre is that all my ebooks are in one place, with whatever info I want to store about them, and can be easily sorted and re-sorted into any order. As I was organizing my books I found some duplicates; now it's easy to check so that doesn't happen again.
On the subject of various types of DRM, as far as I can see the only good thing about Amazon's is not the DRM method itself, but just the fact that Amazon will probably be around for the foreseeable future. I buy mostly from Amazon not because I like their DRM system but because of other things that I prefer about Amazon.
Just considering the DRM types (assuming you're not planning to strip it) I find B&N's infinitely preferable. I always used the same credit card at ereader, Fictionwise, and later B&N. When I finally had to change to a new number (a re-issued card from AMEX because of my number being compromised somehow) I had the choice of either re-downloading my books after changing my CC info at the seller sites or just leaving them as as and keeping a record of my old number and the applicable dates. With encryption based on name and CC there are no device limits, user limits, time limits, or online dependencies. No deregistering/registering devices, releasing licenses, worrying about sellers going out of business, etc. Once you've downloaded a book, you can copy it onto as many devices as you want, whenever you want; all copies are exactly the same.
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