As mentioned by Arpan there are no plans to support ASP.NET Web Parts with MCMS with SP2.
Anyway, today I took some minutes to play around with the web parts using my ASP.NET 2.0 site (see here for details on how to setup such a site) and at least for a read-only website I did not find any issues when MCMS placeholder controls are hosted inside a web part zone.
It's really a very nice user experience if a user is able to arrange the MCMS placeholder controls - which are actually fed with content from the MCMS repository - using drag and drop between predefined web part zones. Very cool!
I'm not sure if the limitation that web parts will not be supported is caused by an incompatiblity in web author or just due to the fact that web parts will not be included in the test suite for MCMS 2002 SP2.
We will see more as soon as SP2 is released. If there are any issues then I assume only in authoring mode. And here a workaround might be either to ensure in the template code that the web part manager display mode is configured as BrowseDisplayMode. This will ensure that the web part content cannot be dragged and dropped as this might cause troubles in authoring mode due to the additional postbacks. We will see as soon as SP2 is available.
Is the code for this sample you built posted anywhere on GDN? It would be real useful.
I haven't uploaded it as it is not supported.
Now after MCMS 2002 SP2 has been released I would like to point you again to an article series I have...
Although not officially supported, MCMS 2002 SP2 works fine with Web Parts as I outlined earlier.
Can I get a copy of this code? I have been asked to temporarily create a Request More Information user control that they can place on any of the template pages on their MCMS 2002 web sites. I stumbled on this and thought it would be a GREAT way to give them a single web part which could be added to any of their pages.
Thanks for your help...
Sorry, the machine I used 6 years ago to test this is gone long and it seems I did not save these test projects.