I would add something about 'This Service Unavailable" messages when trying to run Analyzer, Architect etc. - this is not a 'hang', but is symptomatic of no more available licenses. Sorry I didn't mention this explicitly before. Even the support guys on the phone with me did not know that the system was trying to tell us it had run out of licenses - they had to check the logs. Until a more meaningful error message is provided, perhaps this should be added to the chart too.
Cheers.
Thank you Alessandro for this post. It got me started, and was quite valuable to my education.
However, in my usage case, performance was still quite sluggish, so I tried another approach: I created a SQL-based KPI that selected against the underlying table, which resulted in much better performance. In my testing on a cube with 900K facts, the performance was quite literally more than an order of magnitude faster.
Using SQL with CASE statements, one can derive all of these fields, although the SQL is perhaps even more baroque and complex than even the MDX is.
I believe NOW-1 would give you what you want.