After cutting up some dirty wood I found the chain had got quite blunted and the cutting performance very poor. I decided to try sharpening the chain instead of buying a new one and as it turned out, it was easy to do and the results were very good.
Two bits of advice:
1. You'll need a kit that is the right size for your chain. If you don't know the size, there should be some marking on the side of the teeth on the chain, so check before you buy.
2. Look for some online video guides of how to sharpen a chainsaw. There are plenty available and they were really useful.