I've been looking for a solution to this for some time nom - and I just came accross this :
Custom SharePoint User WebService V1.0 - (useful to switch views depending on the current user's SharePoint groups in Infopath)
Actually the WebService has only one method: GetUserGroupsFromCurrentUser(). This method simply returns the current user's SharePoint Groups.
But there's a build-in SharePoint WebService which does the same?! Yes, that's right! But the built-in service doesn't work with Infopath 2007!
http://ilovesharepoint.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=15260
Read more: http://cglessner.blogspot.com/2008/07/infopath-switch-view-depending-on.html
It really helped me, so I thought others would also find it helpful.