For me, the only major differences between Solaris and Linux are that the Solaris commands and directory layout are vintage 1990 or earlier and that, in particular, the "ps" command isn't what I'm used to. Then again, I don't run GUI Solaris, usually - I'm ssh'ed in.
I did find the Solaris desktop fairly easy to use, if somewhat primitive.
Actually I lied about differences - I build software packages, so I had to learn the difference between building a "pkg" and an RPM http://sunfreeware.com
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