It's never good to see a game developer leave a company - especially one as well-known to the game's community as Cylus is to Vanguard players.
For those unfamiliar with him, he was the game's item designer and has designed many of the items in the game thus far. Just 2 weeks ago, Cylus was part of the Getting to Know the Vanguard Team series, and now on the Fires of Heaven forums he's announced his resignation from Sigil/SoE as of tomorrow.
Cylus has clearly been under a lot of stress during his time at Sigil, as his pot shot at Nino proves, but Nino responded calmly to it, understanding that there's a lot of pent up frustration, no doubt shared by many former and current members of the Vanguard team.
It's definitely a sad day for the Vanguard team; Cylus did an excellent job in his position as part of SoE.