It is well worth getting a fit, most shops will do it for free when you get a bike. IMO there is no such thing as a perfect fit from a shop, they will set you up in a good starting position and from there you will need to fine tune things when you have ridden it for a while.

If it comes down to getting a lower spec bike and a fit, or a high spec bike, then get the low spec with a fit. Its worth it to help avoid injury.