Rating: - Not perfect, but I'm happy with it.
I purchased this mower partially out of spite. I'm sick and tired of having the oil companies run my life, so this seemed like a good chance to deny them access to my wallet when I mow the lawn. All of our other lawn accessories are electric, so with this purchase, I no longer need a gas can or oil.
Having said that, this mower isn't as well-designed as it could be. The cutting height adjustment seems flimsy. Out of the box, our mower kept sinking to its lowest cutting height by itself. I don't know if ours is defective or if they are all like this one. I had to monkey with it for about 15 minutes to get it to stay locked at a height setting. Since then, it has stayed at the cutting height I selected with no additional incidents, but I am not looking forward to having to change the cutting height in the future. For the record, I followed the manual's instructions to set the cutting height but did not attempt to contact Black & Decker for additional help.
Our yard is 1/4 acre and we have very thick burmuda grass. Our lawn had not been mowed for about three weeks prior to this purchase, so the grass was very tall. Our first attempt to mow the whole property ran the mower's battery down several times, so we had to mow in stages and wait for the mower to recharge between attempts. I would guess it took us six mowing sessions with charging time between each session to get the yard back under control. I don't blame the mower for this, but if you are like me and you skip an occasional week during mowing season, don't expect this mower to chew through a lot of tall grass on a single charge.
Since that difficult first cut, the mower has completed the front yard and the back yard with a single charge between the two sessions. I doubt it would have completed the entire property on a single charge, but we always mow the front yard and the back yard on different days, so we'll probably never answer that question.
I love the idea of a cordless electric mower. Although my experience with this one has been limited, I would purchase one again if I had it to do over. It seems a little flimsy and had the height adjustment issue in my case, but it's clean and quiet and seems to meet our needs.

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Rating: - Good but unwieldy
I like my new cordless mower. It works well (but then it should, as it's new!). Mowing without an electric cord is a delight. The only drawback I see, so far, is that the mower is quite heavy, rather cumbersome, and difficult to maneuver. You get quite an upper-body workout while mowing. That said, given the noise and pollution of gas-powered mowers, I would never go back to a non-electric mower.

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Rating: - Good mower
It's good, but it's not a great mower. I replaced a 10 year-old rechargeable Ryobi Mulchinator, which died recently. I have a small area to mow, less than 1/8th of an acre. I'm hoping this mower lasts as long as the Ryobi Mulchinator. So far, here are my observations:

Pro:
- Uses two 12volt batteries, which are much less expensive and more available that the Ryobi's 24volt battery. That's a big advantage. All rechargeable mowers eventually require battery replacement.
- Cuts grass very well, maybe better than the Ryobi ever did, even when new.
- Reasonable price - $369 is not a bad price.
- I like having an external transformer - saves weight on the mower and will be simpler to replace than the Ryobi's.

Con:
- The battery is held in place in part by two styrofoam chunks. This cheap material will never last more than a few years and will have to be replaced. The plastic cover is also cheaply made and will probably crack after a while. The Ryobi was better on both counts.
- There's no charge meter - the Ryobi had one that worked well.
- The overload breaker resets automatically after one minute. There's no manual reset, and it's not user accessible.
- It's heavy. Doesn't bother me, but if you intend to mow a slope, or lack strength, then these lead-acid battery mowers won't work for you. Someday there will be a lightweight lithium-ion battery mower - I'll be the first to buy it.

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Rating: - What a Great Mower
This mower is awesome -- no cords, very little noise, no exhaust fumes, and it does my entire lawn on one charge!
I would recommend this product Black & Decker 19-Inch 24-Volt Cordless Electric Mulching Lawn Mower #CMM1200 to anyone.

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Rating: - Great Mower!
I have a smaller yard in the city (roughly 60x120) and the cordless mower works great!

The mower was fully assembled. All I had to do was unfold the handle and hand-tighten the bolts. It took about 7 hours to do the initial charge, and I keep it plugged in in between mowing so it is always ready to go.

The mower has one large button to easily adjust the cutting height and has plenty of charge to mow my lawn, which usually takes about 40 minutes. The 19-inch cutting width is a hair smaller than my old mower, but not so small as to be annoying. I hardly notice the difference.

Since the mower is not self-propelled it takes a little more effort to get it up inclines, but nothing grueling. The mower is not light, but it rolls easily on large wheels. My 9 year old son was pushing it around our yard after I got it with no problem at all!

I haven't used the bagger yet, but it does a nice job mulch mowing right out of the box.

Some reviews complain about how loud it is, but you can easily talk over it when it is running and it is loads quieter then my old gas mover, which I needed ear protection to use. The electric motor starts and stops on a dime so it is not problem if you have to stop to pick up a stick or some wayward toy.

So, if you have a smaller yard and want a green mower option I would highly recommend this mower.