Sid:
Ryan said Morneau's power compares with that of Kent Hrbek, a great home run hitter and a great-fielding first baseman for the Twins on the 1987 and the 1991 World Series champions.
Hrbek, Career: .199 ISO
Hrbek, through age 25 season: .294 average, .480 slg. .186 ISO
Hrbek, age 25 season: .278/.351/.444, .166 ISO
Morneau, Career: .271 average, .505 slg., .234 ISO
Morneau, age 25 season (this year): .324/.378/.605 slg, .282 ISO.
It's not like I'd be disappointed if Morneau had power like Hrbek's, I suppose. No, wait, I will be disappointed. When it comes to Morneau's power, I don't think Hrbek.
I think KILLER.
Killebrew, Career: .253 ISO
Killebrew, through age 25 Season: .262 average, .528 slg, .266 ISO
Killebrew, age 25 season: .288/.405/.606, .318 ISO (Good God! 
Okay, he's not the Killer, but boy he's a lot closer to Killer powerwise, and I like it. How about we call him Li'l Harmon?
Are these adjusted figures? To play devil's advocate (or Sid's advocate, or TR's advocate, as the case may be), the league SLG% in Morneau's first 3 seasons has been between .427 - .438 (don't know what it is this year, but I imagine it's similar).
By comparison, the league SLG% in Hrbek's career, outside of 1987 and his final season in 1994, was never above .416, and several times was even below .400. Morneau is still better, I imagine, but some kind of adjusted figure like SLG+ would probably have them a little closer.
Of course, this adjustment might also elevate Killebrew's power to another dimension, since the league SLG% over his entire career> was just .392.
Add: The Hardball Times has the AL SLG% at .437 so far this year.
Are these adjusted figures? Hell no! That would ruin everything!
Using Clay Davenport's translated numbers, which adjust for park and era, we have:
.294 -- Killer's career ISO
.239 -- Hrbek's career ISO
.303 -- Morneau's 2006 ISO
Killer is way ahead of Hrbek in terms of hitting for power, and Morneau, at least this season, is a lot more Killebrew than Hrbek.
Morneau certainly doesn't walk as much as Killebrew, though, but these days it's not looking that unlikely that he could be a .300 hitter for a few years.
So they all get scaled upward in the translation? That seems odd, especially since Minnesota parks have consistently received hitter-friendly park factors, and they represent three different eras... could this figure be considered the ISO equivalent of OPS+?
I apologize for being a statistical novice!