Same dilemma recently, Richard. Went with MyFax.com for $10/month. What I liked about it, was that they give you an actual fax number for incoming faxes.
The only times I've had to use it in the last year were for my accountant and for the Teamsters, who always want directions faxed.
The capacity to fax was the next-to-last reason for keeping the land line active. Any day now, the land line will go the way of the 8-track tape... The last reason has to do with NYC-related disaster situations wherein cell phone service is disrupted for long periods of time. Worth that $20/month for a telephone security binkie? Maybe. Maybe not.