My 'alternative' universe. What's yours like?
I said up front that I make a living supporting AIX. As it happens, I am currently contracting for IBM on a customer site, and have in the past been an IBM employee for a number of years.
But with my 20+ years of AIX (mostly outside of IBM) and over 30 years of other UNIX experience including 10 years of Linux in fields such as banking, utility, engineering, education and government, on systems running from micro-processors through departmental minis to Amdahl mainframes, AIX really has been this easy, at least if sensible design (i.e. like the manuals say plus a bit of common sense) has been followed. And it is still improving! (no, this is not a sales pitch, merely my observations).
I will stand my UNIX experience up against anybody else's. When I started working with UNIX in 1978, there were about half-a-dozen UNIX systems in the UK, and the total number of people with any experience in the UK probably did not exceed 100. And I have worked almost continuously with UNIX ever since.
Back to AIX, and no platform is without warts, and as good as I perceive it to be, sometimes you have problems. But where I am currently we have in the area of my responsibility 300+ AIX systems, being thrashed (literally) 24 hours a day, with 10's of TB of data changing on a daily basis, managed by a team of 5 people, some of whom have other responsibilities. On the same site, we have large Linux and Windows deployments, and there is also a Mainframe doing critical work.
Our current uptime on the AIX systems is low at around 60 days (having had some global power work done in the last two months), but normally runs into the 100's of days. In that 60 days, we have had about 8 disk failures out of an estate of about 4000 all of which were handled without any outage (including system disks). In the past, we have had memory failures, with the systems continuing to run until a convenient time to move the workload, and CPU's taken out of service in the same manner. We've also replaced complete RAID adapters (in an HA RAID environment), power supplies and cooling components without losing service. This is BTW, a clustered environment.
We are just about to embark in replacing 100s of RAID adapter cache batteries, and we do not expect to take *any* service impact at all during the work.
I would suggest that if the systems you 'have been forced' to use have been a bad experience, either you are not giving the whole picture (like if you think that you need the latest and greatest Open Source products - which would really be an application problem, not a deficiency of AIX or POWER platform), or there has not been due diligence in setting them up. Get someone who knows what they are doing in on the installation!
I have often found that sites tend to be partisan. Solaris or HP/UX sites often do not embrace AIX enough to understand how to run it properly, and vice-versa. But I do try to keep an open mind, and I do appreciate that I am not as knowledgeable of more recent Solaris or HP/UX systems as I am AIX. But in recent years, I have perceived them to be less innovative than the IBM offering, and when I last has serious work to do on them they just felt like they had been left in the last century when it comes to RAS and sysadmin tasks. But that's my opinion. I'm sure there are other opinions out there.
But I would say that AIX looks destined to the the last Genetic UNIX standing, given HP and Oracle's current attitude towards their products, and Linux still has a way to go in enterprise environments to replace it. I hope so, anyway, as I would like to get to retirement age without losing my career!