if you dont use a whammy bar read this

unfortunately at the moment they're quite expensive. i wouldn't recommend fitting to a guitar thats worth a bit ie. class guitars with history etc , as a lot of routing has to be done to the body of the git

i fitted one to my fender strat which as been modified over the years so isn't really worth anything as an original

i am lucky enough to have an overhead router so i did it myself with diagrams obtained from the evertune website . it does require advance DIY if you're doing it youself

as far as tuning is concerned i've not retuned my guitar since i fitted it and set it up( AUG )
if you do a lot of bending though you have to make sure you're at the end of the ' sweet spot '
else your bends wont happen ..tune just sharp then back off <1/4 turn and pull the slack out of the string( see the evertune vids ) this only needs doing occasionally ( pref just before a gig or recording session just in case the tuning pegs have been compromised )
http://www.evertune.com/bendingvideo/
bottom line is ..it wont go out of tune when you're gigging

if you dont do any bending then once your strings have settled down tune 1/2 turn below just sharp then you should never have to tune again even from a sweaty gig to playing in the open air . Theres no way you can 'sqeeze it out of tune' or hit the E string sharp

the only maintenance is not letting the strings loosen of too much else the bridge will start to move backwards affecting the scale length ( but it wont go out of tune to the extent of 9 slackening turns of the tuning peg )

awesome.. best thing since almost anything
www.evertune.com