It seems like many of the people wanting the 13" MacBook Pro don't really need the Pro at all. A plain, old MacBook would do just fine. In fact, if you look at the specs for the current 13" MBP and the MB you'll see they are very similar machines. The new version will be more powerful but probably not amazingly so.
If you really need power, you need the Pro but I've been using a MacBook in my work as a programmer and have found it to be acceptable. The only reason I'm upgrading to the new MBP (when they come out) is that my screen died and I am doing enough demanding stuff like simultaneously running Photoshop, Netbeans, Terminal, Mail, Safari, Firefox, Virtual Box (where I'm running Windows XP, Outlook, IE6 and Firefox), a webserver and database, Macvim, iChat, Preview and a bunch of smaller utilities, that I can justify the need. But I'm currently running all of that on a 2 year old MacBook with 2GB of RAM and it works. Not super responsive but that is more of a RAM issue and a "multiple years of cruft on the hard drive" issue than anything else. I really suspect that most users could easily get away with a MacBook with a bunch of RAM. Certainly if you find yourself thinking "Do I need the MacBook or the MacBook Pro?" you will probably be just fine with the MacBook.