Of the things discussed in this post, the main area where I would seriously suggest a commercial Common Lisp system even for a newcomer, is if they are interest

Of the things discussed in this post, the main area where I would seriously suggest a commercial Common Lisp system even for a newcomer, is if they are interested in GUIs, either on the development or runtime side. I can recommend LispWorks for those: it has a graphical IDE with graphical debugger, and a very nice cross-platform GUI library with native look-and-feel (called CAPI). I think compared to the open-source options, both of those will result in a lot less pulling out of hair. CommonQt is passable, but CAPI is far less of a hassle, especially for cross-platform deployment. The obvious downside is that LispWorks costs money and is not open-source, so is probably most attractive to people developing a commercial product. Also, in the case of using CAPI, you commit to LispWorks as your implementation.