Hi, we were recently (july 2011) in Uzbekistan and stayed at both places: Antica and Gulnara.
Antica - might be overrated considering the price (50USD doubleroom) but there are not that many guesthouses in Samarkand (as compared to Bukhara) and the place is nice (garden, spacious room, though "oldish" beds). But breakfast is the best we've had: fruit, freshly cooked things, breat, homemade jam, .... not just the fried eggs tea bread that you find elsewhere.
Gulnara - clean and with a good atmosphere, but terrible plumbing. At least in the upstairs, we booked an ensuite room and yes, it did have a bathroom, but with NO running water unless you walked down two floors and asked them to connect the water pump. So don't book an ensuite room, as you will have to go down to the common areas (where the common bathroom is) to wash your hands or teeth...
We complained about that to the owner but he didn't give us a discount, or change our room or anything.
Enjoy Uzbekistan!