Accommodation is all pretty similar in its lack of quality — in particular, in its lack of warmth — here in cold, cold Uyuni. Hotel Avenida is probably above average in this regard, but that's not saying much. The rooms are still bloody freezing at night, and have no heating. When you come to Uyuni, wherever you stay, make sure to bring thermal nightclothes, and a very warm sleeping bag. You'll need it!
Rooms: very cold at night. Otherwise fine.
People: travellers on their way to the Salar de Uyuni, or on their way to somewhere else in Bolivia, just like you.
Staff: brisk, but accommodating enough.
Location: pretty much in the middle of very small Uyuni. Also conveniently next door to the immigration office, for those continuing on to Chile as part of their salt flats tour.
Food / Internet: none.
Hot water: water at any temperature (hot or cold) is only available from 7am to 9pm (this is pretty good for Uyuni!). Hot water is about as good as you can expect in this town: hot enough to be bearable when at low pressure; and freezing cold if you turn the tap up.