How important it is to get a final order about financial issues very much depends upon individual circumstances and the factors which weigh with one spouse may be very different when looked at from the viewpoint of the other spouse. Say, for instance, H and W have no assets and H knows that W is going to remarry as soon as the decree absolute is through. In that case there is probably no major benefit in seeking a financial order. On the other hand, if there are significant assets such as a house or pension(s) then it is usually wise to get a final financial order because the downside if that is ignored is potentially very costly.
In each case it is a matter of weighing up the costs of obtaining the order against the potential costs of doing nothing. Usually it requires taking at least some basic advice in order to make a properly informed decision.
An order can be obtained whether the other side co-operates or not although non co-operation does make the process more costly. Having said that, very few people are non co-operative from beginning to end because quite early on the non co-operative spouse will usually be penalised in costs.