well if u want to be a *nix admin i suggest u work ur way up from solaris, to other flavours on nix and then maybe to linux (redhat etc)
solaris is widely used in larger enterprises, larger enterprises try to stick with same vendor for OS & app combo (not always true though) Try to run it on virtual machine, try vmware.. without frying your monitor, it really help us simulate a lot of stuff and learn somthing worthwhile.. i have win2k3 AD talking to redhat samba, jboss clusters, setup NIS, HA or LoadBalanced servers etc ..
HP-UX, IRIX, AIX, SCO-UNIX, DEC etc are old and you will still find them in huge enterprises but they are dying, HPUX, Solaris, IBM AIX are the only ones which are doing better, solaris no being opensource is just a popular option. But mainly enterprises are shifting to opensource solutions, moving to linux, moving to apache from iplanet, moving from websphere -> jboss, blah blah...