I recollect that when this was previously discussed the concensus was to avoid the overhead of including a JS UI framework because developers may wish to choose something else.
Even with jQueryUI, there are many different configurations available and it doesn't make sense to start to add too much bloat which may not be wanted. A better approach may be to create a new scaffold "Welcome JQueryUI" app which includes some themeroller stuff etc and this app could be maintained by the designers in the community rather than Massimo. The 'no-brainer' way of installing basic jQueryUI is currently to use plug_in_wiki.
