I already mentioned here and here that I love Apex and OWB since they are Oracle database integrated development environments, this is simply because I am an old school SQL and PL/SQL minded person and these two development environments make you feel more powerful, which is IMHO a really cool feeling during chatting with the Java/SOA guys :)
I have been using OWB 11g for some time now and I want to prepare a getting starting material to assist my colleagues. Apex has a two-days developer guide for this purpose, and OWB has its fantastic OTN OBEs.
If you are already aware of the BI fundamentals and Oracle database fundamentals you can go through these 16 11g OWB OBEs within a day or two and than I am pretty sure you will get the feeling I mentioned. As you may know with 11gR1 now OWB and Apex are a part of the standard database installation, so if you have a 11g installation you already have an OWB practice environment, following the first OBE will be enough to initialize your OWB inside your 11g installation.
These OBEs do not only include typical practices but also information on Warehouse Builder 11g architecture, components, BI concepts like Star Schema and Snowflake Schema or Slowly Changing Dimensions. Also here is an additional viewlet which may give you an idea about OWB. Remember what actions you do inside your mappings they will all deploy a standart PL/SQL package, these old friends are your ETL executables for your each BI need. And OWB is a cost-free(database-licence included) option and it is a highly optimized ETL tool which uses Oracle’s SQL capabilities.
And as some readers may be thinking since Oracle bought ODI OWB will be dead soon, no this not true and you may read the future strategy from OWB’s corporate blog here, to my understanding OWB and ODI will be a part of a combined BI solution strategy together, like a coffee and milk together, so this is not a coffee or a tea choise :)