The prefix is helpful, but only in certain conditions.

If you're using the Query Analyzer object viewer or using Enterprise Manager to browse for your stored procedures, then a prefix probably won't help you much.  I don't think it would make it more difficult either. 

Remember that the naming convention for stored procs is for more than just the DBA though.  Developers use these stored procs and in a complex script with many stored procs, tables, views, functions, and other objects, it takes out the ambiguity when looking at a script.  It's especially helpful if you're looking at the script via a text editor, Visual Studio, or something else where you don't have the full support of Query Analyzer or the ability to quickly run a SQL statement every time you see an object name and can't remember what it is.  It won't make or break you, it just makes development easier if you can limit the guesswork.

Good article though.  I'm a big supporter of naming conventions.  I have used several different ones at various client sites and the ones who have a standard and follow it are much easier to support than those who don't -- irregardless of whether they include or discard the prefix.