1. There is no brake! I just don't like to let these little saws wind down on their own. Even the cheap cordlesses have brakes. This Dewalt doesn't.
2. Flimsy construction vs. the other Dewalt 18 volt tools... The shoe, blade guard, handle, etc. all seem fragile. This might be an issue where looks are deceiving, but this saw just doesn't seem to be made by the same manufacturer as the 18v XRP drill.

I didn't drop-test the saw or perform scientific tests, but it did seem to be the weakest link of the 18v line (The XRP drill and recip saw were great!). I suggest anyone considering purchase look long and hard at the way this saw is put together, before purchase. Personally, I would have put up with a more delicate saw, if the thing had a brake. In the end, I wound up buying the 24v saw... much more solidly constructed product. I'll give it four stars since it's fairly solid vs. other 18v tools... just not nearly as tough as Dewalt's 24v saw. In the end, Dewalt still gets my money ;)

DeWalt DW939K 18-Volt 6-1/2" Cordless Circular Saw Kit (Rating: 4.00)
Review : I bought the DW939 a couple of years ago and for the type of work I use it for, it can be a real time saver. I use it mainly to crosscut 2X or rip plywood on smaller jobs. It saves a lot of time by not having to lug around an extension cord, a generator on jobs where no power is available or by having to go out to the job and take measurements first, then do the cutting back at the shop.
To be realistic about things though, I wouldn't mothball your heavy-duty corded 7-1/4" saw just yet.
I've used it to cut 4X4 and 4X6 PT posts several times. I only have to flip them over once to finish the cut and the job is done. The battery run time isn't bad when crosscutting 1X and 2X or ½" plywood but DeWalt must do their battery runtime testing under carefully controlled laboratory conditions because as other owners have stated in their reviews, it's not likely your going to get close to their rated number of cuts per charge with the DW939. So definitely, buy a second battery for continuous use. A fresh sharp blade also helps increase battery performance.
Although the bevel capacity is 50 degrees, from my experience, that is one tough cut for this saw to make in anything more than 5/8" plywood. It's seems just to taxing for the little motor.
Overall, even though it is a bit pricey, I would recommend the DW939 as a go between saw. When used within it's limits, it is excellent on smaller jobs when you want to make a few quick cuts without dragging out the extension cord.

Good worker. (Rating: 4.00)
Review : I have been cutting 2x8s and it does a great job. Especially nice is being able to cut thru the 2*8 at a 45 angel. The blade lock makes changing the blade easy.

The safety latch seems a bit awkward. One has to push the button in before pulling the trigger. For me, the button is in the wrong place and would be easier to push down rather than in. But this is a minor problem.

I haven't used the saw enough to stress test the battery

I haven't used my corded saw since. (Rating: 5.00)
Review : I built a house last year (I paid someone else to do the framing) and, since there was no electricity at first, I bought all the DeWalt 18-Volt tools. There was no problem cutting 2-by lumber, unless it was wet. The battery lasted longer than I expected, but I do have several batteries, so I can get a whole day's work out of them. The torque of the 18 V tools actually exceeded some of my corded ones. I like the balance and the fact that I never have to worry about a cord getting in the way or finding a receptacle. My wife even drove over a set of tools in the case and I bent them back straight and they still work.

Cordless isn't acceptable for occassional use (Rating: 4.00)
Review : The saw is well made and easy to use except for the trigger. I find it difficult to press the safety and the trigger at the same time. Especially when cutting at an odd angle.

I have used it for framing and plywood. The guide is very easy to use and keeps a good straight line. It won't cut completely through a 2x4 at 45 degrees so you'll have to flip the board over and cut from the other side.

However, this is not a saw that is acceptable for occassional use. If the battery is not properly discharged and recharged it will quickly become a doorstop. Ask yourself how often you are really going to use the saw. If it isn't at least once a month then a corded saw would be cheaper. Otherwise you'll be replacing the battery.