Keep in mind that BEA Weblogic Portal (with Workshop IDE) is quite expensive . JBoss Portal is young (relatively new) and is free.
Having used BEA's WL Portal and workshop to develop portals, I would say that for me, I don't think an IDE provides too much value in this area - and thus, having an IDE with a few features targeted at portlets would not make or break a decision to use JBoss Portal. Rather, if you want a low-cost Portal Server that provides a decent baseline set of portal functionality based on JSR168, then JBoss Portal is a good choice. Jetspeed 2 has potential but it's still too complicated.
I'm currently working on a plugin for Eclipse to help create projects for JBoss Portal portlets - it will create the xml files required and generate some skeleton code for a portlet, then be able to bundle them into a WAR you can just dump in your deploy directory on the Appserver. The XML part is done, I'm just reading up on how to programatically create code from a plugin. Then I'll release it to the list. I've been away with work for the last couple of weeks so it's stopped for a bit, but I'm back on it now. Expect something in a week or so, if you can wait that long :)