Hi Phil, again I would agree with Jacqui. Demonstrated use is usually a strong foundation for protection from someone presenting their brand in a manner similar to yours in a way that might confuse the market. However, having worked with clients in this situation, the practical outcome is usually that the cost of the fight is not worth while and they end-up rebranding. Having the brand mark trademarked in the first place will put you in  amuch stronger position to defend your ground.
 

I may be a little biased, but yes I absolutely think a business should register its trademarks whether they've been used for many years or not. Several rights and advantages are awarded that you won't get other wise simply by using the trademark.

• The right to use the trademark...  this is not a guaranteed right simply by using it;
  
• The right to authorise others to use the trademark (for the goods/services you've nominated) - i.e. the right to license the use to someone else;
  
• The right to take trademark infringement action against others. (Without a registered trademark you would be relying on other areas of law to stop people using similar logos, which can be harder to prove)

Plus - by registering you make it difficult for others to register (and therefore gain the right to use) similar logos in your same field of business products/services.

I'll add to this that whilst having a trademark registered is a sound idea you don't need one registered to be allowed to use it unless someone else ends up having the trademark done and makes a claim against you.