I am also a webhoster like you, as well as being a web application developer. I run Oracle, Sybase, and MySQL instances for different size projects.

MySQL is fine for small apps but fails on large apps due to:
lack of referencial integrity support (no cross-checking accross tables for validity of fields)
slower update/insert (but faster select)
no stored procedures (but in MySQL4 beta it is implemented and apparrently works quite well)

That said, most of my customer-support and customer-database work is on MySQL (It is far easier to use).

If you want SQL2000 capability, I suggest you consider Sybase or Oracle on Linux!! Both are much cheaper than SQL2000(even Oracle if you can deal with the added BDA requirements) and does not require a MS box. Sybase 11.9.2 is free and you can get Oracle 8i licenses for $100.00 (or free) if you ask. Sybase is trivial to install and available free.

Oracle can be acquired quite competitively but is not trivial to administer.

MS SQL Server and Sybase are 99% the same thing, having come out of the same development effort betweek sybase and microsoft in the 90s.

Have you considered Postgres? I have not used it but collegues who have used it swear by it. It is fast, cheap, and supports referencial integrity.

hackmare.
roasp.com