I have the Razer mamba and Steelseries Steelpad mouse mat.
The mamba seemed like a great mouse for the first few months, but the battery life is useless for long gaming sessions, and will quickly leave you scrabbling for the charging cord. The more demanding you are of the mouse in regards to sensor dpi and polling rate, the worse the batter life gets, I just leave mine plugged in all the time now, making the charging dock rather redundant. As for the build quality, over the months it has gathered many creaks, rattles and squeaks, particularly when using the left and right mouse clicks. It has got louder and feels like it is grating. Searching on Google for this shows it as a common problem where the lubricant doesn't last long enough. Not really good enough for a £120 mouse.
The steelpad has been in service about the same time as I thought it would last forever and be worth the £30. It has coped pretty well with my daily abuse, but the edge is starting to show signs of wear, and the fact that it needs re-oiling from time to time is a nuisance, I also think the oiling cloth is starting to dry out (even after being kept in its original sealed bag) and I have no idea where/how to replace this.
I guess my summary of both these is that for the outlay, I expected a little more, some of my cheaper peripherals like the logitech G15 (mk1) are still going strong despite a constant hammering, and my roccat kave headset has been subject to much more abuse under the wheels of my swivel chair but still acts as new.