If this was a 2 star hotel, I would probably rate it higher, but it claims to be 4 star, so my rating reflects its performance relative to my expectations for a 4 star hotel.

Location
The location of the hotel is not great because it's on the main road to France (you wouldn't guess that from the promotional photos!). However during the night it is fairly quiet (presumably because the tunnel south of Vielha is closed to trucks at night), and it was therefore easy to sleep with the windows open to let in the cool autumn night air.
The location of Vielha itself it quite convenient, being equidistant from the two main access points to the Aigüestortes i Estany De Sant Maurici National Park.
But I found it quite difficult to select a place to stay that was (a) 4 star, (b) highly rated in Tripadvisor, and (c) open during this shoulder season. My final choice of the Acevi was a compromise and compromises are often disappointing.
Vielha is probably the least attractive of the towns in the area, being the largest and having been overrun by rampant (and in my view poor) development. Finding good food in Vielha is also a challenge, but see my review on "Er Occitan" in Bossost.

Room
I booked a junior spa suite for our 4 night stay, but as that came with only a spa (no shower), we moved to a family suite instead (thanks to the helpful receptionist). There were still "shower issues" though - see below. The room was spacious, comfortable and smartly designed, but looking a little neglected - a broken shower, a damaged toilet seat, a blind that did not open fully, etc. And whoever ordered the desk and the chair obviously never tried them together - I needed to put both cushions from the sofa on the chair in order to be able to sit comfortably at the desk, and I am average height.

Service
This was variable. The morning receptionist and the ever-present waiter were friendly and helpful. But the behind the scenes staff not so. The promised repair of the broken shower never happened; half-used soap was removed and not replaced; the mini-bar was not restocked, etc - small things, but ones that make a difference. [Fortunately I was able to make temporary repairs to the shower myself, to prevent it pointing permanently at the wall!]

Overall
There are some hotel rooms you walk into and immediately feel comfortable and at home. There are others where some thought and care by management would have made it so, but you compromise and accept and live with it. There are others that are just plain not up to scratch. The Acevi was in the middle category, and disappointing, but explains the variabe reviews that it has received on Tripadvisor.

We chose this hotel for our ski holidays in Baqueira-Beret. We wanted to stay in Vielha which 11 km from the ski resort rather than in the resort because in the town you can find much more to do for apre-ski. Vielha is a very nice Spanish town in the mountains. So, the Acevi Val d'Aran hotel is located in the center of Vielha. The hotel offers very good food for dinner (you can take half board). It is a la carte and different every night. Only food is included in the half board scheme. You have to pay for drinks (even for water). I suggest the hotel reconsiders this approach and includes at least water and tea/coffee to the half board scheme. Now, breakfast - this leaves much to be desired for a four star hotel. I would recommend the hotel to enrich their breakfast menu. Rooms. Rooms are small but this is not a problem as they are convenient. If you travel withy spouse or partner ask the hotel to put you in a real double room with a bigger bed. First we were put in a room with a small bed and it was uncomfortable to sleep for two people. Next morning we requested to move us and they did it without any problem. In general the hotel staff is friendly and speaks English.

Excellent value for money. Wonderful location with lots of good hill walking. Would not hesitate to return to the hotel and Vielha.

Wife and I visited this hotel 25.12.09 -> 27.12.09 with friends for the purpose of skiing in nearby Baqueira/Beret.
-Location is spot on with free and easy car parking and walking distance to eateries/entertainment in city centre Viehla.
-Only 15 min drive up the mountain to ski slopes.
-Hotel offers suitable, fresh breakfast for all tastes, shapes and sizes - you won't leave hungry.
-Standard rooms are adequate, clean and comfortable for a couple with ski gear, although hotel offers space to store large equipment.
-Staff/service is pleasant with no fuss attached.
-Sitting room downstairs is inviting with bar, TV and communal board games.

My experience is summarised as so: for a long weekend or short leisure pursuit, this hotel would accommodate most in comfort without many extras.