In this order:
1. A *reliable* graphical FTP client. gFTP is buggy (I almost buggered up some osnews ftp files once while trying upload using drag-n-drop), Nautilus/vfs doesn't cut it, and KBear looks really ugly and uneeded busy (and hasn't been updated for over a year).
2. Windows Media & QuickTime. Sorry, but I need my regular dosage of movie trailers. Real Player works on Linux, but I need QT and WMV/WMA too (and please don't suggest the windows-codecs package for use with VLC/Xine/Mplayer and their browser plugins as these hardly work with what's out there).
3. Audio & Video support for AIM/iChat, Y! & MSN in Gaim or Kopete (I need a multi-protocol app to handle these). I have three webcams here, I gotta use them. Gaim-vv is still alpha quality, and it isn't really part of Gaim's official line.
4. Alsa needs to fix their architecture and/or drivers to automatically include a software mixer if the hardware doesn't have one. There are a gazillion of PCs (and especially laptops) out there with Intel/Via AC97 onboard sound cards that don't support hardware mixing. For these machines, Linux will only serve sound to one application at a time. Using the "dmix" software mixing plugin only satisfies Gstreamer & ESD apps, XMMS and Mplayer (all after tweaking their default settings to use the new "default" virtual Alsa "device"), but there are so many other apps that are not configurable as they use their own OSS/Alsa backend that simply won't even load sometimes, or just won't play any sound (mind you, the "aoss" trick only works with Real Player).
This situation is disgraceful considering that we are in 2004. This is not 1993 with Windows 3.1 and Sound Blaster, people. The Alsa Project should find an automatic solution to this huge problem that degrades the Linux experience down to the floor. Remember, these Via/Intel on board sound cards are everywhere these days. At least 2 out of my 8 PCs here have the problem with Linux (which is not a problem at all with Windows/BeOS btw). Update: I couldn't help myself and emailed the Alsa guys about it.
5. A good home video editor. Kino is closer than others, but still not there yet, plus it's easily crashable.
6. A simpler interface for Gimp. Something like PaintShopPro's. Trying to do some basic image editing with Gimp is a nightmare. PSP's and Photoshop Element's interfaces are much more intuitive for simple stuff, Gimp's is simply not.
7. Easier wi-fi/bluetooth configuration and ability to easily "create networks" with them (share internet connection with other wi-fi or bluetooth devices). Currently this is a lot of hard core unix command-line work on any distro. Even Mac OS X only makes it easy for Wi-Fi, but not for IP over Bluetooth.
8. Library developers should not break their APIs too often. There's nothing more nerve wrecking than trying to satisfy deps by compiling them, and realize that your app doesn't compile because it needs this or other specific version of a library/header. Yuk.
9. Better and more reliable ACPI support. Currently my ATi-based laptop does not awake with any distro I tried (and recent kernels with supposedly "fixed" acpi).
10. Better PalmOS and PocketPC synchronization software that work with the latest models and software (I got a new Clie). Something like "The Missing Sync" available for Mac.
Your needs may vary...