What are people's thoughts on cocktail ottomans?

Assuming you're dealing with a dark brown leather sofa such as the H&M Rugby:

Do you go with a matching leather ottoman?
Contrasting Leather?
Contrasting Fabric?
How large? It seems like most ottomans aren't wide enough to look right in front of wide sofas.
Is a proper table a better idea than the ottoman?



Specifially, what style ottoman would go well with the H&M Rugby in dark brown?