Based on this blog's traffic the IBM i 6.1 upgrade planning checklist is the 3rd highest viewed page. That's encouraging! It's nice to know people are looking at moving to the newer operating systems. It's also a little expected because it people may be moving because end of support for V5R4 is on the horizon, instead of moving to take advantage of new features. I was at a conference many years ago where Frank Soltis joked about the difference between iSeries and pSeries customers. He said that pSeries customers upgraded to the latest AIX version as soon as it was released while iSeries customers upgraded to the 2nd newest release of OS/400. It was true back then and you still see it today.
While no support end date set, it was withdrawn from marketing on May 27, 2011 and if history is indicative of IBM's plans, expect support to end for V5R4 sometime in late 2012. But that doesn't mean that IBM won't offer program support extensions similar to V5R3 which you can get until April 30, 2012. This is all speculation of course and none of that means you shouldn't be looking at new features and understanding how they can help your business.
I strongly encourage you to check out the features of IBM i 7.1 and the prices of Power Systems iron. You get way more bang for your buck than what you used to.