I have the Porter Cable nail gun set (compressor and 2 nailers) and could not be happier. I use them in my profession (home restorer) and they have never let me down - not a single misfire in 2 years. I have no expereince with the DeWalt nailer, but I can tell you from experience their warranty service is world-class. I recently purchased a DW706 (12" dual-bevel compound miter saw) and the blade guard broke (my fault) after about 50 cuts. Dropped off at the local service center and a week later is was brand new - no questions asked.
If, however, you are just looking for something to use on occasion, you might want to consider Harbor Freight (www.harborfreight.com) They have nailer for about $15. Not the best build quality, but it is functional. I picked one up just as a spare, but have never actually used it.
Another place to look is the local newspaper or "Trading Post" type of classified newspapers. I see nailers in our local one all the time for about 75% off retail. Some were used by weekend warriors and others I'm sure are beat to hell. Still, it's worth a look.....Colin