This is a good thread and has given me pause for thought and the ammo to go and do a bit of a net-trawl for Blinkfeed info.
If I can add everything I need to this Blinkfeed, so Facebook, all my email accounts, Twitter plus various forums I am a member of, then I will use it. I definitely don't want it as my first page though and I really don't want it to be 'left' of my home screen. In my opinion, if we are stuck with it having to be there, then I would much rather have the option of deciding where to put it.
After some digging (link below refer), Blinkfeed works by launching the corresponding native app when the icon is tapped, so Twitter in the native Twitter app. The issue is I don't like the native Twitter app as it doesn't offer my the level of granularity I want; I prefer to use Tweetbot instead. I'm stuffed with Blinkfeed unless there is a way to get Blinkfeed to open in an app of my choosing, which there isn't at the moment (although never say never). I can't add in my own RSS feeds, nor can I add in my email accounts.
If I get this phone, I think I will find a launcher and just get rid of Blinkfeed in its entirety as it's not really allowing me the customisation I want.
HTC One hands-on: Sense 5, BlinkFeed and TV - SlashGear