I usually do my initial layout, design and refine my database with MS Access, I can carry it with me on my laptop and pocket pc.

I have a few programs that use access as a backend for over 200 users ( not concurrent ) and as a backend db for a few small sites I host.

Depending on the number of records, the number of concurrent users, the length this will be in use, and the OS it will run on, would be your determining factors.

access will be ok with about 20 concurrent users
access will only manage a db of about 2gb
access would be great for small short term projects
access will only work in a windows environment

anything parameters greater than those should be considered reason enough to switch to Mysql