Stayed at the Silver Tassie for 2 nights in July 2006 to attend a friend's wedding in Letterkenny. In general, the hotel was good, but could stand for a few improvements.
The pluses: Helpful, accommodating staff; delicious breakfast that includes both a continental buffet, as well as a la carte "order from the menu"; bathrooms are spacious with great water pressure and soft, fluffy towels; lots of amenities in room: iron/ironing board, tea/coffee maker, etc.
The minuses: Rooms are a bit shabby. The rugs and bed spreads were stained and worn, and they could all use a thorough steam cleaning (as well as an update); our room was quite dark and stuffy. Since there were no fans or A/C in the rooms, we had to ask the front desk to borrow their fan.
The hotel is located approximately 3 miles from the town of Letterkenny. While you must drive to get into town, it's a very easy drive and the location is right off one of the main roads. It's a good hotel if you're in the area for a night or two.