I'm going to try with and without a RAMDisk for TempDb, as you suggested, compare the two to be sure.

But I'm more confused now than before about disk usage with temporary tables and table variables. Your MS link is for SQL2000, which I have read handled temp tables in RAM differently, so I'm not sure that I believe the answer to Q4 is still true. The other article you linked to suggests that SQL Server caching temporary tables in RAM (when available) has led to the 'legend' that they're stored in RAM instead of disk. What I can gather from various sources is that it seems like both temp tables and variables are always written to tempdb's data files, but are often cached in RAM as well when available, especially when smaller and more frequently accessed (which would still mean that fast storage for TempDb would be required, even when RAM is available). Which doesn't sound all that different from user tables to me.

So this thread has taken a turn, but does anyone have anything recent and definitive that explains exactly where temp tables and table variables are stored (RAM or Disk), and in what scenarios does that depend? If it is stored in RAM when RAM is available, why would Dave Pinal's article I linked to earlier show TempDb pages written to disk?