Seconding the recommendation for a proper combi, I live in 1890s semi and since upgrading from a cheapo B&D drill to my dewalt 796 I haven't needed to borrow my neighbour's corded beast once.
If you're hanging pictures and non-huge shelves/mirrors etc, even in solid wall that'll do. If you're more frequently wanting to drill for large fixings like big floating shelves, tv mounts, cabinets etc., SDS is the way.
Could say in either case it's worth having a good combi, so invest in one of those and if you're still hankering for the SDS, pull the trigger.
What drill do you borrow, mentioned in the OP?