I haven't worked with anything AS/400, so I really can't comment, except maybe to say that I think the AS/400 is IBM's version of the HP 3000 series, which just got canned.

With all that's going on in the Unix server space, IBM really needs to get an AS/400-like VM running on AIX/pSeries, then put the AS/400 out of its misery, like HP did with their 3000 series.

The only reason that I can imagine that IBM still sells AS/400 is because people still buy them (and software, and support contracts into eternity...)
Heck, a few years back, I went into a blinds factory that was still running an IBM Series 36. When I explained that they could replace the system with an IBM Pentium that would be much faster, they said they were "happy" with their System 36.

Maybe that's why Microsoft has finally decided to sell software subscriptions. So companies will finally give up on old DOS machines, and there won't be some goob running Windows NT 3.51 in 2020 (but there will be).

Glen