First of all lets say the only reason you should be in Borgarnes is that you are on your way to somewhere else. That said th hotel was very clean and comfortable with the feel of an american business hotel. There is an excellent hot tub on each end of the hotel, perfect for unwinding after a day of hiking in nearby Thingvellir. There is an onsite restaurant as well as a couple of options in town. We did not eat at the hotel so i cannot comment on the quality, though it looked quite nice.

An added bonus, the views of the mountains from the back of the hotel are excellent.

We stayed twice at Hotel Hamar during our trip.
The staff is very nice and the hotel looks good with great views. Every room enjoys a little terrace which is great.
Breakfast was good (extra) and diner was ok although quite expensive.
The rooms were clean and modern (bathroom) but there is a problem in a couple of them: the cap of the bathroom sink does not stay open. We had this problem both times we stayed there, but we told the front desk and they gave us another room. However, this should be fixed since it seems to be a recurring problem. Also, the shower leaks to the rest of the bathroom from underneath the doors.
There is wi-fi in the room however it is not included in the hotel price and it is quite expensive.
There are also hot tubs outdoors which my friends told me were nice.

Borganes is not the nicest town in Iceland, but the Hamar is fortunately 5km away. Take route 1 out of town going north, and look for the red-roofed mansion on the hill, signposted for the golf club. Drive up to the red-roofed mansion, but turn right before you get there to a ghastly-looking motel. That's it. Now, despite the traditionally awful Icelandic architecture, this really isn't bad. The rooms are fine, the restaurant good (but very expensive) and the landlady a real gem - charming, funny, helpful and welcoming. Oh, and the hot tub is great!

We went there for a weekend, bought a package including full dinner at the restaurant. The hotel was not busy but still the kitchen managed to serve us a good dinner and the waiters did a good job. The location is very quiet and we got a excellent rest. If need to relex for two or three day this is a good option, there is a decent golf course beside the hotel, and all services in the town of Borgarnes 2 km away. Pricing was fair. So overall a nice experience.