The Magic Mouse is great, but it does have a couple issues. My biggest problem... Connection issues. The good news, this is usually caused by a simple problem. Battery fitment.
Test your Mouse:
1. Life your Magic Mouse about 1" above your desk surface.
2. Drop your Magic Mouse onto your desk.
3. Watch to see if your mouse drop it's connection.
4. If it does... this may be the fix for you. (see below)
5 Second Fix:
1. Remove battery cover.
2. GENTLY apply a slight bed to the battery cover of your Magic Mouse.
3. Re-attach battery cover.
It only takes the slightest of bends to keep the batteries secure. In my experience, this completely resolved my connectivity issues, cost nothing and took about 5 seconds to complete.
DISCLAIMER: This is not professional advice. This is a simple DIY fix that is not for everyone. Bend at your own risk :)