[wp-testers] is_post_type not working correctly

[hedwig at senzafineonline.net]

I spend a lot in the last weeks setting up my custom post types and  
taxonomies and making my site work flawlessly with them but after  
upgrading to RC1 I noticed everywhere in my theme where I used  
is_post_type to determine what post type was being used to display  
different content wasn't working so it would display all the content  
regardless of post type.

In short, does anyone else had this problem with this function? and  
if so, knows how to fix this problem?