>But if a candidate is motivated to take a job because they get to use shiny new technology, i would suggest that they are not, in fact, a good candidate. In my experience, magpieism is associated with weaker programmers; not the very worst, but second quartile, say - people who get very engaged with superficial details, but don't think about deeper things.

You want engineers who love to grow, learn and solve problems. Startups in general have rather boring problems to solve compared to large companies. Learning and mastering a new technology however is a problem space that startups can provide their engineers.