The database size is near 0.7 TB, tables are spread into several files, we use joins very heavily (sometimes with up to 7-8 tables), we use stored procedures sometimes, some pages have more than 10-15 queries, we have 150+ million page views per month, the website has public pages and millions of pages (in different modules: groups, profiles, jobs, classifieds, message box, online shops, Q&A, website wide search, ledger based credit accounting for specific activities,... ) receive new users from search results.
I have used several databases (Oracle, MS-SQL, MySQL, PostgreSQL) and in my opinion MySQL does a good job for non-business critical applications.
For business applications (Core Banking) we were forced to use MS-SQL but it could not handle the job (billions of records) so we convinced the bank to back off and use Oracle. I would never go with either MySQL or PostgreSQL for that application (not even MS-SQL). They basically don't have the necessary tools and capabilities (hot backup, two way transactions, SAN clustering, ...) for the purpose. But for non-critical applications MySQL is just fine.