I installed a Newall C80 3-axis DRO on my vertical mill just a few months after getting it set up in the shop, and have found it to be indespensible. I was so impressed with it that a year later, I bought another C80 for my 13x40 lathe. I invested in the 2nd C80 simply because of the experience with the first one, and because I'm certain Newall's scales are pretty much bullet-proof. Living out in the sticks makes getting service such a PITA, which is another consideration.
I don't mind paying for quality - within reason - and would rather cry once than regret cheaping-out when a product repeatedly lets me down over the course of the years. I have no regrets in having installed a DRO on the lathe, even though I don't feel nearly as justified with the investment as I did with the mill's DRO. However, since I don't use coolant on the lathe, I'm wondering if a less expensive DRO with glass scales wouldn't have served my purposes just as well?
I'm fixing to find out, as I've just purchased a 2nd lathe which came with a Sino DRO installed, and the electrician - looking for a warm place to work with our 1*F temps & wind this morning - is coming out to wire it into a Hitachi VFD.