I'll make this as balanced as possible, giving both positives and negatives. On the principle that the final thing you read is the one that sticks the most, so as not to be accused of being deliberately negative I will list the negatives before the positives.
Negatives:
Cleanliness - Windows with cobwebs and dead insects. In any holiday accommodation the bathroom is the most important from a cleanliness perspective, and as you can see from the photos this left a lot to be desired - mould on the bath tiles and dirt on the mirror being the most obvious.
Workmanship - Some of this is very poor. My own DIY skills significantly surpass the quality of work that has gone into parts of this property even though I don't work in the building trade. Photos show the mess that was made of the bathroom's sink and its Velux window frame. All the Velux windows upstairs have suffered the same fate because they were simply fitted and then abandoned instead of finishing the job by treating with several coats of good quality varnish. Perhaps you can get away with leaving wood untreated in properties in dry air locations such as the Swiss Alps, but in the British Isles (and especially on the west coast of Ireland) that is a recipe for disaster, and you can see the result for yourself. Also I seriously doubt that the wiring of the overhead lights in the kitchen would pass a Building Control inspection - the roses are suspended below the ceiling by the wiring itself. The upstairs light switch has been installed at the end of the stud wall that separates the bathroom from one of the bedrooms but is so narrow that the two doorframes overlap the switch's housing (i.e. the owner would need to remove the doorframes just to unscrew the switch's cover plate). Although this is a stud wall, both the copper pipe and the electrical wiring for the power shower have been routed over the tiles in plain view rather than buried inside the wall (which would also reduce any danger of splashed water getting into the unit at their entry point). Although it is a power shower, it has the poorest pressure of any shower I have ever used.
Bedrooms - Described as "double bedrooms" in the property's listing, they are in fact all twin rooms. This is obvious from the listing's photos for all but one room, where the photo appears to show a double bed but in reality it is two single beds pushed together and a double quilt laid on top. My wife and I did not enjoy even this small comfort - the beds were separated and made up as pure singles when we arrived.
Health - If you suffer from asthma, be aware that as with many properties in Donegal the living room in this one has an open fire that has probably mostly burned turf - certainly the smell of it pervaded all of downstairs when we arrived and some serious airing was needed just to clear the air even in the kitchen beside it.
Fridge - So small that a normal 2 litre bottle of milk is too fat to fit in the door pockets; we had to move the bottom-most glass shelf so as to allow a milk bottle to sit in the vegetable bucket.
Positives:
Workmanship - A top quality set of units constructed from 9-ply plywood has been built into the kitchen, with a Stanley oil-fired range installed into it. The kitchen table is large and very solid, as befits a kitchen of this size. If you lack the confidence to use the range for cooking, there are a couple of portable electric cookers that you can use (we just used the range).
Welcome - Monica left us a lovely welcoming note plus a bottle of wine and a box of chocolate fingers.
Cosiness - Whereas on first arrival the property felt rather uninviting, even though it was the height of summer, once the range had been fired up and run for a day at a low temperature the character of the place changed completely; the kitchen very much became the centre of the house and we were happy to entertain guests there.
Summary:
My impression is that at some point someone invested in modernising this property but ran out of funds before the project was completed. In reality, a relatively minor investment of money and effort could make a significant impact on its overall presentation and allow the owners to raise their rental rates (which I would say at present are reasonable for this property in its current condition). At the end of the day, notwithstanding its shortcomings we warmed to the place and enjoyed our stay in Gleann Cholm Cille.