Very powerful once you're set up - discarding a card to ready Host Spider, and by extension your hero, is good value.
Especially valuable at the end of late game All Systems Go! turns: attack, use attack interface, ready with Host Spider, Thwart, use Thwart interface, ready interfaces with All Systems Go, ready with Host Spider, attack, use attack interface, Command to ready Host Spider to ready hero, Thwart, use Thwart interface.
If you don't need that much Thwarting, or on earlier turns, you've also got the option to draw a card for an unused interface, which is great. Don't sleep on this card!