Hello,
is is accepted to work with Nikon Lenses?
I mean is there any quality issues?
I have a lot of expensive Nikon lenses with IS and i am wondering, if it is possible to work with them, with an adapter.

yes, you need at minimum a mechanical adapter and non 'G' Nikkor lenses. there ARE some adapters that work with 'G' (G lenses have no manually adjustable aperture ring) lenses, but they cost around euro 100.

i use nikon lenses on my T2i's.

Yes, it's entirely acceptable.

Seeing as auto-focus is pretty useless in Movie mode with these cameras, you really don't lose much by having manual-only lenses. In fact, limiting yourself to manual-only lenses opens up a whole world of cheap, quality options particularly for prime lenses.

As Panagiotis said, it is preferable to have Nikon lenses with an aperture ring on the body (non-G lenses) for use with Canon bodies. There are adaptors available for G lenses but they are much more fiddly and expensive (espescially if you want one for each lens).

Nikon lenses will work fine but unless I'm missing something VR will not work.