When I had to buy a new mouse late last year I was deciding between the G500 and the Mamba.
I avoided the G500 for one of the reasons in this review, I had a G5 at one point and absolutely hated how the mouse wheel would tilt when I pressed it. The G500 appeared to have a similar wheel design so I passed.
The Mamba, when I first used it, had an absolutely amazing grip and possibly one of the best wheels since the original Boomslang (which has the best wheel I've ever used on a mouse, though the mouse was fairly lacking for comfort).
To make a long story short, I ended up returning the Mamba about a month ago. Ultimately it was due to reasons of build quality. The 3 major strikes against it were:
1: The wheel started squeaking. Apparently this is a common issue with the mouse. There is some friction present in the internal mechanism, that causes the plastic-on-plastic to start squeaking. There are corrections you can make by taking the mouse apart (which can be done without breaking any seals), but I never bothered.
2: The rubber side-grips started peeling off. As much as people compare this mouse to the Deathadder, it really does not feel like it at all. The side-grips are a huge improvement over the Deathadder, both for the indentions and the textured grip. Again, I am sure I could have super-glued the grips back down but I didn't bother.
3: The battery plain sucks. I primarily used the mouse wired, but would run on battery when Playing World of Warcraft because I didn't really care about the latent feel for that game. Having hardly used the battery, I was surprised when I started getting maybe 2 hours of usage outa the thing after only a couple of months.
Thankfully I had bought a return plan with the Mamba at the place where I purchased it, something I rarely do. I have since swapped it out for the G500 and I could not be happier.
I am still not a fan of tilt-wheels but the way it's implemented on the G500 is much closer to the wheel on the G9. Since it's got a flat feel to it I hardly ever inadvertently tilt it.
I was suspicious at the tiny cluster of side buttons but honestly they have such a great tactile feel. I much prefer them to the side buttons on the mamba (which I also had no complaints about), and especially the garbage that passes as side-buttons on the G9(x).
So in the end, I swapped out the over-priced and poorly built Mamba for the much better G500. It was literally half of the cost, and I can see myself using it until it falls apart. Which, if my MX518 is any indication, may be a good decade from now.