Thanks for reporting your Problems.
But I'm a bit Confused about some of your Problems.
fieldset name won't accept spaces
This should take spaces have a look http://sofis.gesis.org/sofiswiki/Spezial:SolrSearch/Projekte
This is our Fieldset definition from our wiki, maybe there is an error in your definition ?
$wgSolrFields = array(
new SolrSearchFieldSet('Projekte', 'Titel; Personen; id', 'Titel; Personen und Authoren; SOFIS-Nr. (Erfassungs-Nr.)', ' AND category:Projekte', 'AND'),
new SolrSearchFieldSet('Institutionen', 'name; Inst-ID;ort', 'Name; Institutions-Nr.;Ort', ' AND category:Institution', 'AND')
search form and results are messed up in Vector skin (fixed with /table from below)
this should be fixed now in the SVN, sometimes my friend User:Schuellersa gets a bit confused by his SolrStore Versions and commits the wrong one (This is the 3. time we fix it now :)
Prompted to 'Create the page [fieldset name] on this wiki!'
This is really new to me, could you please post your $wgSolrFields definition?
trying to run refreshdata from semantic mediawiki/maintenance
We are working on that, could you try the newest svn version
This seems to be the same error Extension_talk:SolrStore#Unexpected_XML_tag_doc