Well, depending on how long ago you read about enhancements, the subway now has lifts to all platforms and toilets have been improved on platforms 1/3. Retail units now fill the space where the original BR booking hall was, this is the main pedestrian route to/from the adjacent Bus Interchange, the Frenchgate Shopping Centre and thus access to the Town Centre. New bike racks/shelters have been placed near the station front.
Additional platforms (on the west side / goods lines area) would definitely reduce delays to XC and Northern services to/ from Sheffield, as congestion caused by slightly late running East Coast Kings Cross to York stoppers, Newcastle/Edinburgh and Leeds services can result in XC Reading to Newcastle services taking 5 - 10 minutes to travel the last half mile into a platform. Sheffield to Hull services are often subjected to similar waits, though they can use platform 3 more easily. However this work would be quite expensive as the space available is limited.