@El. Reg. Don't agree!
"AIX was always the laggard when it came to commercial-grade Unixes"
You need to qualify this. When AIX 3.1 on the RS/6000 was first launced back in 1990, it wa streets ahead of any other commercial UNIX. It has a logical volume manager, an integrated system management utility (remember, this was a time when sysadm ruled the roost for most UNIXes), dynamically loadable device drivers, and was one of the first UNIXes that did a good job of merging SystemV with BSD flavours of commands and libraries (SUN's way of doing this was less transparent).
With the SP/2 in the mid 90's IBM moved AIX into high-performance computing (Deep Blue et. al)
In the late 90's, they were up there with 64 bit systems, and had a nearly seamless 32/64 bit strategy that meant that the kernel you booted did not have to match the binary you were running.
For absolutely years, AIX was the leader in the Gartner manageability surveys.
Power4 systems, available in the early 2000's implemented hardware partitioning. I'm not sure whether HP had this on the Superdome (or whatever they were called at the time), but I remember this being a real marketing differentiator at the time. Power4 also had SMT of a kind.
Power5 systems, available 2004/2005 implemented I/O virtualization, sub-cpu partitioning, and dynamic hardware allocation and de-allocation (this might have been possible on Power4, I can't remember exactly).
IBM were slow on SMP, the initial work being done by Bull with the G/J30s, but when you have systems with single CPUs running as fast as your competitors SMP boxes, what was the hurry.
The only thing that I believe that Sun had was the containers, and to tell you the truth, I never worked at a customer where this caused a problem.
So tell me. What else were IBM lagging behind their competitors.