This is a good summary of the role of title tags and domain names in Search Engine Optimisation.

I would add also, click-through-rate will be improved with better title tags and meta descriptions:

• If your title tag just says “Welcome” and your competitors nicely describe their products, which one is more likely to be clicked on?
• If your meta description is just a list of keywords what does this actually tell the customer? Much better to promote benefits such as free delivery, fast delivery etc.