Keep in mind that one query is not always like the next one… 100 optimized queries in an application even against a large database of information is likely going to be less processor intensive than 10 not well thought out queries against less data in a smaller database. Also it all comes down to how well MySQL settings are optimized for the type of data being stored. Do you have MySQL 4.x’s (or newer) caching, buffers and such optimized well, or are you using pretty stock settings that likely are not going to do your script justice no matter how well the script performs its queries. Saying 6 queries is better than 100 queries is not a valid assumption as there are WAY too many variables.
Also ALWAYS keep in mind that a sites performance when you hit a site may have to do more with so many other variables than simply, “well they are running EE and their site seems slow”. Is the server hardware overloaded with too much traffic in general (ie: apache/php/mysq even drive I/O functions or TCP/IP stack overhead is too much for the hardware its running on currently), are they being hit with a reference to their site from Slashdot or similar and again hitting hardware/OS/other resource limits.
You could go on and on. ilounge.com will soon be moving to a load balanced web server solution because they simply have too much traffic to be handled by the hardware they are currently on, macdailynews.com just recently moved to new server hardware because their site traffic had outgrown what they were running on before. A performance issue with EE or other scripts (ad banner tracking software) they are running? Maybe. But the bottom line is everything from the OS, scripts, server applications, hardware and network all have to be considered. Impossible to say EE can handle x visitors per second/minute/hour/month, because there are too many other things unrelated to the script that might affect that 
EDIT: When I say “EE” above, you could insert any application name in there. Scripts rely heavily on the underlying techology that are processing them.