[grandiego]

I have a client (banking sector) which "recently" (5 years ago) started with AIX since they already had POWER systems running IBM i (i.e. modern AS/400), and had to select a Unix for a new vendor's EFT system; it was reasonable to use the (almost) same hardware and provider.

Another similar client is using Solaris (Sparc) for an analogous application; they are using it since 1996, I think because Sun (Oracle) always provided an easy migration path, so the applications didn't need to be ported.

As in most medium/big enterprises, in both cases the hardware/software price is not the main decision driver, but (IMO) it is the support/SLA, compliance checklists, and overall risk management.

BTW, in these cases Linux is also used for more "internet oriented" applications.