Some games must have a memory card to play and have DLC.
According to Kotaku Japan, six of the Japanese launch titles for the Vita will require a memory card: Uncharted: Golden Abyss, Disgaea 3, @Field, Hot Shots Golf 6, Monster Raider, and Dream Club Zero Portable. By required, it means absolutely required; the games won't even boot if you don't have a memory card.
On the flip side, the remainder of the launch titles won't require memory cards, meaning all data will be saved directly to the game cards. Sony, however, has revealed that games that save directly to the game card won't support DLC. Whether this means that games that don't require a memory card can save to a memory card and thus get DLC is still up in the air. On the list of games that don't require memory cards is Asphalt: Injection, Ultimate Marvel vs. Capcom 3, F1 2011, Dynasty Warriors Musou Next, Shin Kamaitachi no Yoru, Dark Quest, Shinobodo 2, Power Smash 3, BlazBlue Continuum Shift Extend, The Michael Jackson Experience, Mah-Jong Fight Club, Let's Try Bass Fishing: Fish On Next, and Lord of Apocalypse.
Sony announced the new proprietary storage media, which has prices ranging from ¥2,200/$29/£18 (for a 4GB card) to ¥9,500/$125/£78 (for a 32GB card). Compared to Sony's latest medium used for PSP Go additional storage, the Memory Stick Micro, a 32GB card is approximately $40, while a Memory Stick Pro Duo (the original PSP proprietary medium) is approximately $130 for a 32GB card (Sony brand). It should be noted though that these prices are only conversions of the Japanese yen pricing and not announced prices for Europe and the United States.
A few non-memory card details were also revealed. The Vita won't support video-out, but will support Remote Play for music and videos.
PSP games can also be visually upgraded through bilinear filtering. This option can also be turned on or off.
The list of pre-built in apps at launch are Welcome Park (essentially a tutorial), Party (group chatting), Photo & Camera, Music, Video, Near (which allows Vita users to connect to other nearby Vita users), Browser, Group Messaging, Friend, Trophy, PS Store, Remote Play, Content Management and Settings.
The Vita will also automatically search for a WiFi spot to connect to. If it can't connect, it'll switch to 3G (if you have a 3G system, obviously). If a new WiFi spot becomes present, however, the Vita will not automatically try to connect to it.
The Vita web browser will also support Java and HTML5 at launch, but not Flash. There will also apparently be no Game Archives (meaning PSOne Classics and PC Engine/TurboGrafx games) at launch as well, but these will apparently be added later on.
Sony is also looking into a way for PSP owners to transfer their save data to the Vita. Rumors of vouchers for current PSP game owners to receive a discount off Playstation Store versions of their PSP games are also in the air.
There will also be an officially Portable Charger by Sony, which reportedly doubles the battery life on the Vita.
Music and images will have to be transferred via linking your Vita to your computer, since there is no Memory Stick or SD card slots and the new proprietary media isn't supported on any PCs (as far as I know).