No that is no problem, I think. From the sql-clients point of view, SELECT foo FROM .. just the same as SELECT tags->bla AS foo FROM .. The AS construct makes it transparent for the client if the tag comes from the hstore or from a normal column. This is why you can just write <Filter>[lit] = 'yes'</Filter>, no matter where 'lit' comes from.
Ah, thanks. I have now switched the live lighting.xml file to use hstore, yay. The hikebike style is to follow, but that will take a lot more time.
Cheers Colin