My basic site, which is unoptimised but receives almost no traffic, reports:
Executed Queries: 67 | Used memory: Init: 27.6 MB | Header: 31.9 MB | Footer: 32.8 MB | Page generated in: 2.871 seconds.
According to GD Press Tools:
That's an incredible number of queries and a big chunk of memory just to load the dashboard, but I've only experienced that 'premature end of headers' a few times. I could never figure out what it was, but now it makes sense.
In contrast, another site I'm working on, which I hope will get at least a few hundred hits per day or more, uses at most 4-5 MB of memory, less than 10 queries, and finishes in about 300 ms. It's based on the Dwoo templating engine.