I've owned this machine for over 1 year and overall I'm happy with it. Initial set up was fairly simple and mostly involved cleaning up the rust preventative and dialing in the head (more on this later). This mill comes with the "3 bolt modification" already performed on the head.
I had purchased the power feed unit and installed it right away. The only issue was that I had to modify the small bracket that holds DRO cover. It's nice to have a rapid traverse.
The initial jobs I performed with the machine were very simple and did not immediately highlight a problem with the head and column. I made an assumption that the column would be square to the table both in the X and Y directions. It was not. I found that I could not square up a block of aluminum. Over a 2" distance the block was nearly 0.005" out of square in the Y direction. I removed the head and found nothing obviously amiss, however there were quite a few sharp edges on the vertical slide primarily on the edges of the slots where the hold down bolts pass through. I removed the sharp edges with an old honing stone. After reassembly and making a test cut, there was no change.
At this point I began to carefully examine the squareness of the column. What I found was that it was out in both the X and Y directions. To align the column, I removed the head to make it easier to crank the slide up and down. Using a machinist square and loosening the 4 bolts at the base of the column I found it very difficult to get consistent readings in the X direction. Something was still not right. It turns out that the gib on the vertical slide could not be adjusted properly for two reasons. The first were some burrs on the gib itself, and the second, it was about 1/2" too long. Having fixed both of these issues the column adjusted as one would expect. After reassembly and tramming in the head there was still some out of squareness in the Y direction. I thought I was going to have to make some shims, but re-tightening the 4 bolts brought the column in square. The table has a bit of a dip in the center which makes tramming interesting but the machine will cut squarely. It is also important to note that the column on this machine is not super rigid (though adequate for the size of the machine) and when making adjustments in the Y direction, the weight of the head needs to be on the column.
There was one other issue with the column. The top portion of the dovetail on the right side was not scraped very well and there are tool marks on the dovetail. This is at the extreme upper limit of the travel and I left it alone, but it does bind when the gib is properly adjusted. At some point it will need to be scraped in.
Having made these adjustments, the mill machines very nice for it's size and I'm quite happy with it. The issues with the gib on the vertical slide were not expected, but the problems were in my favor, meaning I didn't need to order a new part to repair it. I did not contact Grizzly support since the machine was out of warranty by the time I discovered it and I really didn't think there was much they could do over the phone/email for these problems. I have contacted them about other issues and they respond promptly.
It was a bit of work to get the machine to mill properly, but it was worth the effort and I like using it.