…is demonstrated, comprehensive generosity in relation to the cause.
“Good with people”, “sales experience”, and “willing to work for a percentage of money raised” (yikes!) are typically the characteristics that rank most highly among nonprofits seeking development staff, but I actually would view each of these three as detriments, not advantages.
- Someone who is “good with people” may end up being liked by your champions, but when s/he finally leaves your organization (often at your behest), your champions, upon learning of the departure, will say things like, “Ah, that’s too bad. Really nice person.” If you hire a really nice person to do your development work, they will be, um, really nice to your champions.
- Someone who has “sales experience” likely has the wrong set of experience for the next generation of development. Coaching is the important skill, that is, helping the champion grow in relation to the cause in their sphere of influence. Selling your nonprofit these days is like selling real estate: just not a lot moving out there…
- Someone who is willing to work for a percentage of money raised has just been incentivized to all kinds of bad behavior. See “sales experience”, above.
Instead, when looking for a development person, start by asking your most mature champion–the one who is already owning the cause in his or her sphere of influence, already giving their time, money, education, passion, attention, and lifestyle to the cause–to take the position. Ask them to replicate themselves. Tell them they’re not there just to raise money but rather to replicate themselves. Hire teachers. Trainers. Coaches. Anyone who loves your cause and knows how to get others active in it comprehensively.
And that last word is key: If they’re not already giving generously financially in relation to the cause as a percentage of their income, don’t expect them to be able to motivate others to do the same. Jeff Brooks notes this great post from Seth Godin on this very subject. Read it and rewrite your position posting for the development officer you’re seeking to hire.
Do the Word 
Being comprehensively generous and being able to successfully replicate seem like two different things. Are you thinking of them separately, or are you including replication in your definition of comprehensive generosity?
Good question, Batesy. I tend to see them as connected for Christians. But they certainly are distinguishable from one another, yes.