I've been a MU member for about 15 years and find it extremely helpful. Some of the benefits I personally find useful are:
- Unspecified instrument insurance up to £2000 including all risks and travelling cover. For insurance over and above the £2k you need additional cover from e.g. Newmoon insurance (discussed elsewhere on this forum).
- Public Liability Insurance up to £10 million cover (so if someone trips over your melodeon case at a workshop or gig, you are covered).
- Very comprehensive knowledge and advice for legal aspects of contracts (for performing, teaching, etc.) and full support if something goes wrong.
- Links to medical assistance e.g. for injuries affecting your playing. I used this when I sustained a thumb injury a few months ago.
- Very informative regular magazine.