We had three valuations on our investment property recently (the one we are currently living in) and two valuations were identical and around what we expected. The third was $30k lower. They all had a good sticky beak, a good chat with me about what we'd done since buying it and future planned renovations. The first two were much more thorough though and took a lot of measurements. The third guy, the lowest valuation, just wanted a chat I reckon!

My advice is have it clean and presentable but I wouldn't bother fixing minor things up.