I have one and used it for around 4-5 months, absolutely loved it. As said it takes a bit of getting used to but within a day or two it becomes second nature. very comfortable to use imo (but thats a personal thing and you wont know till you try it)
Drivers were great, had no problems on windows 7 64bit. Build quality was excellent.
Only reason I stopped using it is because I stopped playing World of warcraft but when I start playing again I will definately be reinstalling the naga