SD cards.
I have a 16GB card in my Hero and have had no issues with it ....despite it being a 'cheaper' carphonewarehouse own branded one!!
Best chargers and Screen Protector
I have the original / official in-car and extra mains charger from HTC ... both are good, although you may need to take note that the Hero's connection is NOT actually a mini usb but an EXT USB!
HTC Chargers – Mini USB or EXT-USB | Mobile Fun Blog
You may want to go for the "HTC TC P300 International Travel Charger Pack".
http://www.mobilefun.co.uk/htc-tc-p300-p18232.htm
My case is the flexishield skin. Nice and slim ... and one that doesn't add weight or a large size to my trouser pocket!
FlexiShield Skin For The HTC Hero - Black
As for a screen protector, I have always found invisibleSHIELD to be the best ... and extremely thin so it doesn't interfere with the touch screen functionality.
You may have noticed that my links are all to the mobilefun website. I have found their service to be excellent and pricing to be very competitive!