crossing your legs and using your soul plates (the grind plates on either side of the wheels) is really, really fun and is one of the sick things about roller blading. those types of grinds allow you to grind on really high shit and you can balance for a long time. you can do skier slides, but unless you angle our skates to do a royal or far you will totally look like a kid trying to do shit on blades that he does on skis and not taking advantage of your souls. i don't mind that at all, but some incliners really hate on kids who do that. plus they're actually harder than you would expect (really easy to miss the plate) and its a little harder to balance.
if you're looking to cross train for skiing, then skier slides are a great way to improve balance, switch ups, 2 on/off, etc..
if you're looking to really get into inlining because you really want to become an inline, play around with all sorts of grinds.
here's an edit my friends and i made. we are all pretty bad at inlining but it gives you a good look at some traditional inline grinds and also some that look just like skiing:
and here's a Vinny Minton segment to show you how sick using your souls is. scope 1:15: