The problem with cross-mounted HDD's is cable management behind them. I know, nobody can see them, but in my case, I really had to stuff the cables down to get the side panel on, which is not good for the connectors on the cables or the drives. I wish...
Power 4 drives from one P/S connection, right-angle plugs are perfect for cross-mounted drives, tremendous improvement in cable management and apprearance (see below)
Absolutely none. The only improvements I could even think of would be different models with more/less connectors, or possibly a modular version (although the latter would negatively impact the appearance)