I bought a Makita XNB01Z brad nailer about 4 months ago on ebay and have used it extensively to nail frames together. I am driving 18 ga. galvanized 32 mm brad nails. I purchased the nailer, batteries, and charger separately for a total price about $370 U.S.
I've had 1 jam with it in about 6000 nails driven. That was on the last nail in a bunch that managed to hit the slit just a bit off center and folded. I had to take the head apart to remove it. This was easily done with the allen wrench supplied.
The only significant complaint I have is that it is a bit heavier than I would like to use.
Positives:
1. it has a "tap" mode that really speeds up frame assembly
2. There is a light focused fairly well on the area to be nailed
3. It is easily adjustable to drive the nail deep or shallow as desired
4. batteries can be purchased with a range of capacity. 3000 mah is adequate. I got 6000 mah but they are larger and add to the weight of the nailer.
With due diligence, good brad nails can be purchased for about $2.50 U.S. per thousand. I've bought 2 packs of 5000 so far.
Makita XNB01Z nailer - $230
Makita LXT 3000 mah batteries 2 for @$70
Makita DC1830 charger - $72