Always start with the production release unless you have specific reason to start with beta- releases. 4.0 is stable, and 4.1 cant be guarenteed since its still going thru beta phase. When you use 4.0, try using INNODB type tables. Use the features, use foreign keys, indexes, rollback and commit features. These features weren't included in the old-style MyISAM type tables. When 4.1 becomes a production release, see what features are added, either u can upgrade or dont bother if not need to. I'm using 4.0 and its working like a charm for me. You only use the beta version of any s/w if and only if the feature u dearly need is available in the beta version and not in the release version. Anyhow, thats my take on the issue.