Should I do some tidying up
Haha... that's a tough question to answer
I built my own computer, and because it had a clear sided case, I had to ensure that the wires were neatly tied down, etc. So, if your case has a clear side, then yes.
Also, neat wires enhance the air flow aroung the computer case, so if you love over-clocking your computer, neater cables may mean that you have better cooling capabilities.
At the end of the day, it's totally up to you. I had a computer with a mini-sized case, but since I didn't overclock, and it didn't have a clear side, I was happy to let it remain in a mess.
However, if you do intend on tidying up, I would recommend that you unplug all the wires, from both ends, and then start prioritizing which wire you want at the bottom most, etc. I use twist-ties to tie unneeded power cables to the slot right below the CD drive.