The screen packs a QuadHD resolution, for a pitch of around 490ppi. The extra size - and especially extra depth - allows Motorola to pack on a behemoth of a battery which should give exceptional battery life, but to be truthful it's another so-so device bearing the Nexus branding.
An expensive one too. With an expected launch price of US$649 it's barely cheaper than the far more capable Galaxy Note 4, although it is US$100 cheaper than the entry-level iPhone 6 Plus. The days of the Nexus being the cheap option are gone, it would seem.
Of the three QuadHD devices that have been released so far the Nexus impresses me the least. The LG G3 offers more flexibility and is far easier on the pocket; whilst the Note 4 remains the phablet to beat, with it's S-pen, expandibility and added hardware and software bundles.
The only obvious reason for picking the Nexus 6 is the likely speed with which it will receive updates as Android 5.0 is refreshed.
Of course once the phone arrives it may work so well that it redeems these failings. However my early experience with the Note 4 suggests that there is little left on the table to improve.
Google is likely to continue offering the Nexus 5, as the 6 appeals to too small a niche market to standalone.