I am considering the upgrade to L5, and am wondering, does it install over L4 preserving layouts, settings, filters, etc., or does it do a new install and one must start all over?
does it install over L4 preserving layouts, settings, filters, etc
Yes it does keep everything.
filters
Graham is right. Everything from L4 is kept — however, there are some OT morphology changes in L5 which will probably break visual filters based on Hebrew morphology. The filters will still be there, but you'll need to edit them for L5. Everything else should work just fine.
