Who does not need ETTL, can buy the YN560 (II or better III) - the flashes are otherwise virtually identical
Those who like to 1/8000 could, should pick up the YN-568EX II.
For me the YN565EX was the perfect introduction.
The flash is quite huge and also consumes quite a lot of electricity. Fortunately, there is the Sanyo Eneloop batteries with whom one does not have to fret (correct charger as Technoline BC 700 provided). When in his Canon has a built-in flash, you can ignite the YN5xx about this (S1 and S2, with and without pre-flash). Really fun, it makes the flash wirelessly trigger the Yongnuo RF-603 - so you have a higher reliability and above all more control over the light, because you do not need the frontal mounting lightning. Of the Yongnuo RF-603, I have three, because you can remotely trigger the camera on it (including the half-point pressure of the trigger.) - At the same time with wireless flash triggering.
Studio flashes can usually settle down only to 1/32 - the YN5xx up to 1/128 and this setting you also need really.
If you are looking for a new flash for its camera, for me not the question of whether or not a Yongnuo, but only some. I have in the meantime a second Yongnuo (the YN560 III), because I've noticed that I rarely successful use ETTL and usually lightning manually.