N91 features a whopping 4GB hard drive and an integrated music player that supports a number of file formats. The phone also offers a 2-megapixel camera, Bluetooth, and Wi-Fi. But the phone is very heavy, its camera has no flash, and it's very sluggish in performing its tasks. Though large and heavy by phone standards, the N91 feels good in hand and oozes quality thanks to its beautiful stainless steel casing. This triband GSM smartphone has a 4 gig hard drive which holds approximately 1,000 songs, similar to the higher capacity iPod nano. It supports MP3, WMA and AAC formats among others and can sync to iTunes on the Mac and Windows Media Player 10 on Windows.

The keypad of the phone is not exactly user friendly. The keys are pretty thin and will be a nuisance typing out an SMS or e-mail, though you will manage to type out phone numbers with a little bit of pain. The phone has a joystick and four buttons on the outside other than the audio controller, two of which are selection and options buttons and the other two are to make and receive calls. The phone has a button at the top right side for revealing the main menu and a volume control on the top left under which is placed a decent loud speaker. The upper side of the phone has a "hold slider" like those seen on MP3 players basically to lock the keypad. There is also a power button which doubles as a profile selection and a stereo handsfree jack or headset connector.

Music playback through the Nokia N91's speakers was ok. It was a bit unbalanced since the speakers are located on only the left side; using the included headset improved the experience greatly. Though it offers some great features, such as an integrated hard drive and music player, but it is very slow and priced on the higher side.