I had the N-7260 in my Dell Insprion 15R, and wasn't even getting half the download speed I should on my 2.4ghz N network, no matter what drivers, card settings, or router settings I used. (This was despite the wireless connection status to the router being reported as expected for my network, at 130mbps). Dell even replaced the N-7260 with a new one, no change. I was considering returning the computer for refund, but decided to instead try replacing the N-7260 with the Intel Centrino Advanced N-6205 that works well for me on my Lenovo Thinkpad W530. (I had also considered a Dell card with an Atheros-based chipset.) Bought a brand new N-6205 from an excellent eBay merchant for $16, installed it, and what a world of difference! Speedtest result immediately doubled from 23mbps download to 46. Then I made a few adjustments to the pc network settings (basically disabling QOS and the "topology" options) and card settings so that it mimicked the settings on the Lenovo, and that raised it to 57, same as the Lenovo, and what should be expected given my cable tier. FWIW, the two laptops are using different drivers for the N-6205...they both seem fine.
I was skeptical that switching to a different card would help, but it turned out to be a 100% solution! More in my earlier post: