"Too large for a phone" is a matter of opinion. This is exactly the size of phone I've been waiting for. I want as large a screen as possible, without making it impossible to hold it to my ear for my (very occasional) voice calls, or conveniently carry it in a holster or (less often) a pocket.
For me, a phone being tiny is of little value. Give me vast amounts of screen space, a large physical keyboard with hard keys with spacing and some travel distance, and a huge battery that won't run out even if I spend all day using it heavily in areas with poor signal. The Dell Streak isn't what I want, having only the screen space but not the physical keyboard and an unknown battery (and an obsolete OS), but the size? Perfect.
"Not useful for serious business"? Depends on your business. Much of my business is coordinating employees via email and text message, keeping records in spreadsheets and simple text documents, and occasionally consulting and searching through previous emails and web-based resources. A smartphone with a 5" screen, a reasonable array of apps, and a keyboard that lets me do 50wpm, is just fine for this.
Even my T-Mobile Sidekick was adequate for most of my business needs, despite the dubious browser and poor screen, thanks to the ultra-quick app switching and utterly fabulous hard keyboard unmatched by any other device. If Microsoft hadn't bought the platform, stripped it of development resources, and left it to die, I might still be using it.
Sure, this large a phone isn't for everyone. But that's one of the lovely things about an open OS - you have choices in hardware. I'd rather use iPhone OS, it's a far smoother user experience, but where am I going to find an iPhone with a 4-5" screen? or a physical keyboard? or running on a carrier other than AT&T?
