Hello
If you are going to use Infopath 2007, you can built browser enabled forms with out using the downlevel tool.
But remember there are list of controls which are not supported in the browser enabled forms.
For more info read the article
http://www.wildwires.com/Blog/PermaLink,guid,8cd25fe3-c225-4ce4-b606-c4b1d90c5a32.aspx
Kalyan G Reddy
Infopath MVP 2007 and 2008