It's a mixed blessing. SD, old-school, 480i NTSC signals hid things nobody wanted to see! Many announcers that looked like they'd stood still in time or were gracefully aging, for example, in HD look not only like they've hit the wall, but the wall fell on them too. Plus, SD shows are still shown and most of them look disastrous on a big screen.
Still, the racing in HD, if done with care and good colour balance, looks amazing.