Power strip, preferably on the wall just above the bench is one thing I wish I had (and plan to add).
Vice is awesome to have and I've gotten quite a bit of use out of mine, it's a larger, inexpensive harbor freight model and it's been doing great so far.
I think I used 5/8" plywood for the top of mine, something heavy/strong enough that if you're pounding on something you don't have to worry about the top taking much damage. I also built mine entirely w/ screws, if a piece ever needs to be replaced, or I want to re-design a certain aspect I can just take it apart.
Ability to fasten to the wall - I didn't do this with mine and the first time I went to use the vice - yeah not so good lol.
Biggest thing is probably height and depth - I made mine about as deep as I had room for so I could store stuff along the back of it and still have room to work on items towards the front half.
I have a couple of these mounted to the wall above the bench (under my cabinets) to hold misc hardware, electrical parts, etc and they work awesome -
http://www.northerntool.com/shop/to...-racks+stack-on-multi-drawer-storage-cabinets
I bought a composite (plastic) pegboard kit from NorthernTool that I mounted behind my bench on the wall - similar to this
http://www.northerntool.com/shop/tools/product_200320589_200320589 but it was only 2 smaller sheets (maybe 8sqft total or so, not sure exactly) and probably a few less accessories. I'm Sure you can do the same w/ regular pegboard and piece together accessories, but I think I paid $30 or so and it's worked out awesome, the bins are great for storing parts while working on something, and various other odds and ends, and then I keep some of my most used tools up there so I dont have to go digging in the the toolchests.