Well I'm quarter Irish and many of their records were destroyed by fire in 1921 and my other 75% is descended from Paisley weavers. Even at the start of the industrial revolution, Paisley already had a population of 4,500 and such records as exist do not give much information so I've got stuck at the fourth or fifth generations with most of my ancestry lines. Though I did discover in my paternal lineage (Cunningham) a great great great grandfather by the name of John McKenzie who was a soldier in the Lanarkshire militia. Jane Hamilton, the daughter of a Paisley weaver, married John McKenzie at the Glasgow gaelic chapel in 1803 which suggests he may have been of highland origin. Their daughter Isabella McKenzie became a Cunningham by marriage.
By contrast my wife's ancestry is from rural south-west Scotland where there were fewer people and more detailed records, and some of her ancestors owned farms, so I have been able to trace some of her ancestry lines back to the late 1600's.
A tip I would offer if you are researching Scottish ancestors is that you will often find two indentically named people in the same place around the same time. At first this can be daunting as you can't be sure which one was your ancestor but if you are able to go back another two generations you often find they were cousins, due to the practice of naming the eldest son after the paternal grandfather.