Do you think the g700s justifies the extra £20 over the g700
I would say No, not unless you really like snazzy paint jobs and an 8 trillion dpi setting!
I can't even recall what other added features the S has over the 700...
Basically, the new surface feels nice, but the 700 is fine as it is.
I won my 700s, so it cost me bugger all to discover the joys... However, I always want more buttons - Could do with that same left-side 3-set on the right as well.. and it doesn't have pretty lights all over it!
Both 700 models are pretty sound, though - The design fits my large-ish hand well (I sort-of palm/hybrid my mice), buttons are easy to hit, never hit the wrong one, software is stupidly easy to work with and ties in with yoru other Logitech G products. The weight is great, even though it's not adjustable, the scroll wheel clutch is useful, profile switching is just where I want it, 14 buttons all fully customisable. Cordless/corded idea works great and in daily use the battery lasts a good few days between charges.
The only thing I really dislike is the cutout for the thumb. Doesn't work for me - I can get cramp sometimes.
The other mouse I like, which is corded, is the Coolermaster Storm Inferno.
It's a bit short for large-handed palmers but nice and wide, four basic extra buttons but you can also customise most of the others. I think the only one you cannot is the rear thumb one, which is permanently assigned to "Quick-Fire Macro Tactics Multiplier", or somesuch. Basically a SHIFT key for 1 or 2 key combinations, again which are assigned to macros, keyboard commands, application functions, etc.
The Inferno is light, but feels solid, has 4 profiles, on-board memory, pretty lights and effects, good grip surface, up to about 5000dpi, twin lasers, yadda yadda.
It really is a toss-up between which of these two I feel like, every time I boot the PC up.
I also have a Roccat Kova[+], but that's a bit naff for gaming.