Staying here at the moment. As others have mentioned, first impressions aren't great, the exterior looks incredibly dated (to the point where if I didn't have a confirmed, non-refundable booking, I probably would have turned around and walked straight back to the terminal and found somewhere else), the lobby/hallways are equally spartan looking too.
Rooms are a little nicer with some newish furniture. Staff seem very pleasant and I was upgraded to a junior suite, which is a good size but the fit out is pretty basic, although I think the room I had at the Hilton Paris Opera in town could have fitted inside it several times over.. Fairly interesting airport view, but no executive lounge or proactively offered replacement option, which is pretty disappointing as I had an evening to kill before my flight. I can cope with staying somewhere that makes me feel like i'm in a 1970s movie if at least there's a lounge with a decent spread *Cough* Hilton London Olympia *Cough* . I wish Hilton would try and do a bit of a better job here, or make it clearer when booking that a particular property has no lounge.
Don't think I will rush back to be honest, really the only great aspect was the rock bottom rate and convenience. Nowhere near as nice as the Hilton Charles de Gaulle Airport I stayed at on my way into Paris, which in turn was nowhere near as good as the Hilton London Heathrow T5 from the night before.