We booked relatively late, so the room we occupied was the only one available for our dates and it was on the second floor (there are no lifts, by the way). But what a room! We had an enormous bed, a bathroom with shower over the bath (toiletries such as shampoo, conditioner and shower gel provided), and a small kitchenette which was well equipped, despite its size. The only thing missing was an oven, but we had a full-sized hob, toaster, microwave and dishwasher. No need to eat out in the evening if you didn't want to. There was also a hair dryer, and a fan for warmer weather. The towels were changed every day and house-keeping even tidied away the cups and glasses we'd left out to dry on the draining board.
Breakfast was included in the price, for which you have to walk a few yards around the corner to the Black Boy Inn, so not much of a problem there. The choices were enormous, ranging from a full cooked breakfast and other hot food, to a large selection of cereals, fruit, yogurt, pastries, fruit juices, tea, coffee and toast.
Checking in is also at the Black Boy Inn. Parking could be an issue at busier times of year as there's nothing on site at either Tŷ Dre or the Black Boy. Some of the nearby public car parks are free between 4:30pm and 10am, which is where we had to park on our first night, once we'd unloaded our luggage (parking on double yellow lines for a short time). At check-in, we were told to ask about a parking permit when we had breakfast the next morning, as they have a certain number of free permits for the car park on the quayside next to the castle. This is just a few minutes walk from both Tŷ Dre and the Black Boy Inn and we were lucky enough to be allocated one when we asked. As we were doing a lot of sight-seeing, it wouldn't have mattered if we'd had to use the public car parks as we were always on the road by 10am and not back till after 4:30pm.
There are plenty of places to eat out in Caernarfon if you don't feel like cooking, including the Black Boy Inn itself. We ate there one night but thought it was a bit overpriced for what we had and weren't overly impressed with the quality, either.
On the whole, a great place to stay and we'd go there again in the future.