I'm 6 hours in but I didn't take the master key when I created my character I then consumed a Fire Soul instead of handing it to the woman.

I did get a couple of lucky drops; Demon's Greataxe and Black Knights sword.

I just restarted and found that the beginning part of the game that took me about four hours only took me around 40 minutes the second time through.

I'm a lot better off now, I'm a bit higher level with more humanity and it just feels like a fresh start on a new game. I was getting pretty frustrated, so in that regard it was definitely worth it for me to restart.

Master key is meh for me, prefer hunting around for keys etc.
Got a good feeling when I could open a door somewhere later because I bought the residence key from the first merchant at the start.
 
The fire soul is handy tho, +1 estus is ace!

The master key would have helped me earlier on but as I have gone about 30+ hours into the game, i dont need it anymore as I have either found the keys or am past the part where its useful. The sword though is a random drop, as my friend got it while i got their halbred, which is not my main weapon :D Unless you like or want to use that sword later, i would restart just to get the better start on the game as most people probably had a frustrating start. Think the only reason i didn't do as bad as others have said theirs was because i spent the week prior beating demons on NG+++.. man that was not fun.