Hi,
I have installed 2 sets on milling machines and one on a lathe, and I have the scales for both my shapers here to install it on them as well.
I would recommend installing the X scale on the front of the table so you don't loose any travel. I did a right up a while ago here about installing it on the front.
http://www.hobby-machinist.com/show...-of-table-HM50-52-Grizzly-3616-3617&highlight=
As for buying one, I bought 2 from Meister off ebay and the other from the Sino guy on ebay. Both have great customer service and arrive quick to your door. They are pretty well all the same, but are a lot cheaper than DRO Pro's, from memory the 2 axis is around $400 and the 3 axis is around $550. Over the years I have only heard one complaint which was a broken scale through postage which was from the Sino guy (which could happen to anyone) and it was replaced promptly.
This Sino fellow will upgrade your scales to slim line for $20 an axis extra or up grade to 0.001 scale for $20 an axis extra.
I highly recommend both these sellers.
If your like most including me, it all seems high tech and a daunting task when buying your first one, but after you get one and install it you will see how simple they really are. The scales are very robust in construction and the cables come shielded from swarf and coolant. The main screen will come with a clear plastic protective cover on brands standard. I ordered an extra one with the Meister's, but have never needed it in 4 + years.
I have had these running for 4-5 years and never had a problem. I am pretty sure they are all coming out the same factory, just with different names and screen layouts, so it is more about saving a few dollars when looking to buy one. The prices have come down a lot over the years, when I bought mine back then it cost me $2150 for the 2 X 3 axis Meister sets with 7 scales.
Dave