Don, I'm just a little more than a hundred miles into an SE 6-speed install on the '04 SEEG, but if it's an even better experience on the '00 SERG, then I can't save my pennies fast enough!
I read with some concern the reports of engine lugging, etc. at highway speeds from others, but decided to do it anyway because the bike is going to see some significant highway miles this year thinking I'd just have to dink with the primary gearing, or change pipes, or both, if the bike felt overly sluggish. But even with the Rineharts, the bike pulls just fine in 6th from 2500rpm (about 65/70, or so) on up into the triple digits ... in a 25mph headwind, two-up, even. You know you're in an overdrive gear, sorta like you know it when your car or truck hits OD, and I can see downshifting when a quick pass is needed, but still, the torque is there to pull the bike in the OD gear.
So, I'm looking forward to the trips that are planned and the bike and me both having a little less physical wear and tear that another 400 or 500rpm can bring to a day's ride. Is it cost justified? No. But is anything we ever do to these bikes (maybe outside the original pipe, air cleaner and custom tune mods to get them running like they should have in the first place)? I just know I'm already wishing I'd have done it a long time ago.