I stayed at the Beudy Hywel with my wife and our 9 month old baby for a week in Dec 2013, and with regards to the cottage, our stay was near perfect!
Some points that I must mention:
1. Very tastefully decorated, top quality modern furnishings and kitchen equipment, huge LCD makes you feel at home. Everything is there to make you not miss home! The welcome wine was a pleasant surprise :-)
2. Lovely owner, Mrs. Banner - she was so very helpful in making sure we were comfortable - right from directions (which aren't easy if not guided properly!) to the setup of the place, especially for our 9 month old... Very warm and friendly owner!
3. The views - mesmerising! the cottage is at a height so the views of the town / village, especially at night are breathtaking! The sheep in the fields and the horses next door make the stay very pleasing!
4. Open until midnight huge Tesco and Morrisons near Caernarfon (within 3-4 miles) - so very handy for supplies!
5. Mrs. Banner lives just across the field, so in case of any help, there's nothing to worry about.
Some additional info (these didn't bother us, but worth noting!):
1. No washing machine, though there are laundrettes within close enough driving distance.
2. If you're traveling in winters, I would strongly recommend driving your own car as the approach to the cottage is 'through' 2 fields which are literally part of the property, but don't have any lights, quite understandably. Being new to the place, you don't want to be walking through the dark!
Overall - a FANTASTIC stay, I would give this 5 stars on 5 - the additional info is just something to be aware of to make sure there aren't any surprises!