Two of us stayed at Matīss's lovely flat over a long weekend and we loved it. The photos are beautiful and accurately reflect the apartment -- we were delighted with the attention to detail in the place: the lighting, the candles, the beautiful gold moulding on the walls, and the paintings. The flat was very light and airy and was a great place to rest after full days of walking around Riga. The only very slight negative is that it's on the fifth floor with no elevator, but you get used to it! The apartment is also more like a 20-25 minute walk from the Old Town but it doesn't feel far; we never used public transport during our stay, except for travel to and from the airport, but there are plenty of buses heading into town.
A nice touch was that Matīss left us a bowl of Serenade chocolates that you'll see all around Riga from the famous Latvian chocolatier, Laima. You can actually visit the chocolate factory just round the corner from the flat -- not a must-see, but a nice distraction and for 7 euros you get to sample hot chocolate, some of their wrapped chocolates and have a chocolate bar printed. You should also check out Rocket Bean Roastery (also on Miera Iela), which is a very chilled out coffee shop with excellent coffee and a great place to start your mornings. You should also pick up the map from the till by "Like a Local" because it has some great recommendations in there that we hadn't heard about elsewhere.