@Lieuwe: Thanks for the mirror lockup tip. So much I already learned and so much more to learn!
I agree that getting sharper pictures is a constant battle.
BTW, my SD card seems to be REALLY fast. In the manual Canon writes that using RAW + JPG you can only take 3 pictures continuously until the internal buffer is full and the frame rate drops from its maximum of 3.7 FPS. Using RAW you get 6 (double!), using JPG you get 26 (or was it 36?).
I found the doubling surprising and so measured it myself and got 3 with RAW+ JPG and 6 with RAW only, just as Canon writes. I measured 3.6 frames per second, again what Canon writes (inside the error of measurement). But with JPG I get "unlimited". In other words, my card is so fast, I can shoot at 3.7 pictures per second and the camera does not have to slow down for the card at all

.
I am still very happy with the choice of the 550 based on my needs. BTW, its funny, all the stuff I knew the price for (boy, kit lens etc) was very cheap, the rest not quite so

. Oh well, all in all it is still very good price for bying in a shop with assistance etc.
JAMF, I will need to lookup the brand.
Unfortunately the shop did not have the #1 accessory you need for DSLRs in stock, namely time

. I am both learning theory and shooting quite a few pictures and gaining experience, but "deep" raw editing for now is outside of what I can afford time-wise. I did a bit of fiddling with the "Tonwertkurve" (output intensity versus input intensity) in the supplied program ("Digital Photo Professional"). That program seems to be good enough for me now.