Whilst it was daunting going on my own I did have some spare time to explore the city!..
The best thing about going with work (apart from that it was free) was that I explored lots of areas that I wouldn't normally have visited as all my meetings were so spread out - I literally went to every corner of Milan.
All the tourist sites were in the centre and were very close to each other - In one afternoon I managed to see the Cathedral, the parks, the shops, the theatre and the castle and arch!... admittingly I was exhausted afterwards from all the walking but for a whistlestop tour I certainly packed it in!
Here are a few iphone pics of the touristy bits :)