The paper notes that while the Air's 1.6 and 1.8GHz Core 2 Duos are the slowest in the MacBook lineup, they should be more than enough for everything except heavy-duty applications, such as video editing. The presence of Bluetooth and 802.11n Wi-Fi are likewise appreciated, though the paper was told by Apple CEO Steve Jobs that cellular wireless was deliberately omitted, since it would both occupy more room and limit people to a single carrier. It is the obsession with size that causes problems with the Air, primarily in terms of the battery, which can only officially be replaced by Apple. This might be less important except that the tested battery performance was three hours and 40 minutes at best, and an hour less when watching a feature-length movie rented from iTunes. Apple promises as much as five hours in its marketing. There are also just three ports on the system, divided between stereo, USB and micro-DVI connections. There is no FireWire port, unlike most Macs, and users cannot connect an Ethernet cable without a USB adapter, which may rob some people of other peripherals they want to use. Lastly, the Air does not have any built-in optical drive, and so must either use an external one or Apple's new Remote Disc feature. USA Today comments that this actually works fairly well, and among other things lets users migrate files via Wi-Fi, and install from DVD drives on both Mac and Windows machines. The main issue is compatibility with third-party firewall software, something Apple says it is trying to resolve.