Craft alone - is it worth it?
I would go with no. The portions are really sized for sharing. The bigger the group, the more fun it is - I probably wouldn't go with a smaller group than four, personally.
For solo dining, I think composed plates is the way to go - in that area, similar food, same owner - do Gramercy Tavern or Craftbar. Also Aldea, which many others liked more than I did so I'll bow to the collective opinion. Or head downtown to Colicchio & Sons - TC's actually in the kitchen these days, I hear, since his CdC left.
I'm sure there have been a number of "best places to dine alone" threads already, though...
42 E 20th St, New York, NY 10003
900 Broadway, New York, NY 10003
Colicchio & Sons
85 10th Ave, New York, NY 10011
Craft is great but, as noted, best with a group. I'd suggest that you try Hearth. Marco Canora was the orignal chef de cuisine at Craft, working with TomC. The food is wonderful. Of equal importance for a single diner, Hearth has four seats at the pass in the kitchen, that are perfect for single diners. It is like sitting at the bar, but better, since you have a full view of the open kitchen and a chance to have a dialogue with the chef as dishes are composed for service. Can't be beat for a solo diner.