I've SS'd for several years both on and off road. I would say that for an 8 mile commute it will make very little difference at all other than, as you say, mechanical simplicity.
Fixed wheel cycling does carry some benefits such as supposedly smoothing out your pedalling stroke but unless you're training for racing that would also be debatable.
IMHO the best place to SS is off-road where the single gear encourages you to keep momentum going especially up short climbs, so overall you will tend to ride a bit faster. You may well find this on the road to a certain extent but in my experience less so.
One thing you can try before bothering to convert your bike is to just select one gear and stick with that for the whole ride in both directions. Purists will argue that this is not the same but it will give you an idea if you are going to able to get on with riding SS and also the gear ratio that you are likely to need for the sort of terrain and riding you do.
One thing I would say is that generally you will be able to ride a bigger gear than you might think. When people start to SS they usually think that the gear that they need is the one that will get them up the hills. What you will find however is that the main limiting factor is spinning out on the descents and even slight downhills. You will also be surprised that you will be able to climb hills in a bigger gear than maybe you will select when you have several to choose from.
Give it a go and see how you get on.