I got a new guitar with double lock sistem, which they said was the best sistem. However, I find it very difficult to tune my guitar and when I have to unlock the guitar it takes a lot of time. Also when a string is broken, it is very hard to change it. I'm always affraid a string will brake during the a concert...

A double-locking tremolo has advantages and disadvantages. This device is based on tension. When it is unlocked and you are tuning using the headstock tuners, as you tune a string tighter, the system loosens. So you have to tune multiple times before it is set. Then lock it. Then use your fine tuners and do the same. While it does take some time getting used to, this system is great for staying in tune.

If you break a string on stage, you'll need another guitar. If you want to play in Drop D or C or any other tuning, you'll need another guitar. As they're based on tension, they have to be set up for a specific tuning.

People generally love these or hate these. I think they're great to have, but having a guitar without one is a good idea too.