Why black instead of white like the rest of your woodwork?

Leave the oak as-is. It works nicely with the oak stair treads. It also is a nice contrast from the wrought iron balusters. The existing scheme is a good expression of the materials present - ie wrought iron = black, Oak = natural. Paint will chip and eventually look awful. What you have now is quite sophisticated and elegant.

What you have is a very timeless look. What you want to do is very trendy and will not be an asset to your home in 10 years.

Thanks all. I am still unsure. I love the black rail with white spindles, as it would be in the kitchen, but unsure if I will like the black rail with the iron balusters in the foyer. I am surprised so many of you think this is a trend I will regret later. That makes me reconsider painting it any color, but I'm still not loving the oak rail.