The Hilton at Herndon is a above average but typical airport hotel. Conveniently located near the airport and with good facilities. The hotel is pleasant in the lobby and communal areas with good WiFi access in most areas.
The rooms are spacious and in good repair with good furnishings. The Executive Lounge is acceptable although a little small and busy in the mornings for breakfast, so get there early. The breakfast on offer is more than adequate.
The gym facilities are excellent: great sized area with plenty of equipment and all pretty up to date and modern.
The bar and restaurant food was a let down though. The lunch buffet, while very reasonably priced, was pretty bland and most of the food on offer was dried out and mushy, even at the start of the service. The bar restaurant wasn't much better for dinner. Reasonable menu, but again the food was a let down: the steaks in particular being too and overcooked. I guess that is to be expected from an airport hotel bar!
However, as a pleasant hotel for an overnight stay, it's one of the better airport hotels I've stayed at.