Just the other week I went from a performance MX to a G502 X Lightspeed (not the plus with the RGB because I wanted better battery life).
It's a reasonably similar shape, it's certainly comfy enough, the hump isn't as high as the performance MX which I think suits me better, but the tail of the mouse extends a bit deeper into the hand.
It's got lots of extra buttons and still has the infinite scroll wheel. Over 15 days it's used only 25% of its battery so I think I'll get about 2 months out of it on desktop only use.
I don't like the rubber sides, they feel a little sticky rather than grippy at times. I definitely appreciate the weight reduction (165g on the MX down to 100g on the g502 X). The tracking is WAY smoother and better than the performance MX, I actually didn't realise just how bad that was. I think my performance MX didn't like this mousemat though, but it's possibly the increased polling rate.
Anyway, G502 X might be one to check out. I'd wait for some kind of deal on it though, it's definitely overpriced at full retail.