If you are like me, you may be looking at this tool and thinking "why would I buy a grinder, no battery, etc."? This was an excellent deal for me, here's what I did: I bought a Hitachi 18v driver / drill combo set that included a carry bag, charger, and 2 batteries. The batteries are fully interchangeable, both the Ni and the Li-ion, between the Hitachi tools. This saved me about $120.
The grinder is lightweight, powerful, and the Lithium ion batteries you may use from another set are very lightweight. I have used the grinder on concrete, for cutting the bottoms of door jambs, tile, and other applications. It has plenty of power to spare, and does a superb job.
I have become a real fan of Hitachi tools over the last year. I started with the combo set I mentioned above, and have expanded my tool set to include almost all of Hitachi's 18v cordless tools (reciprocating saw, etc.), as well as a miter saw and a few other power tools. I recommend looking at the reviews for each type of tool you are considering, but let me tell you that I saved a lot of money and have totally interchangeable tools using just a few batteries (which is where most of the expense is). I highly recommend Hitachi 18v cordless tools and this grinder in particular.