PeterT, do you have a surface grinder? What sort of results are you getting?
An important aspect of surface grinding (and nearly every other aspect of work shop activity) is the skill of the operator. A capable operator, working with that "entry level grinder" can produce excellent results. Give that same person a really good grinder and the results may only be slightly better, but they'll be able to accomplish it faster. Provide that same high end surface grinder to a rookie - and the results probably won't be much better than if they had a POS grinder. Like everything else we do, grinding is somewhat of an art.
100-200 years ago, people were achieving incredible results using equipment and tool that were vastly inferior to the cheapest tools that we have today - there was a greater reliance on the skill of the person and they spent a lot more time.
My SG is nothing special, but there is no doubt that the skill of the operator is the #1 short coming.
The graduation of 0.001" or 0.0001" really isn't that a big deal (a good hand, and suitable support equipment for precise measuring could probably turn out tenth results all day).