I should qualify the following answers: LinuxMCE is a lot more than a media center. It is a Smart Home platform, one of the first of its kind. While some of the media aspects that you want are not yet available, we do a lot of things that currently nobody else has under one roof.
1. We do not have a transcoding gateway to cell phones, yet. We do have a complete mobile orbiter system that can be used inside the house to control anything inside the house. We use bluetooth dongles on each media director to sense when they've gone from one room to another, so that Follow Me functionality can be done. The mobile orbiter also has offline operation, so that when outside the house, any scenarios defined as mobile orbiter scenarios can be executed (lights on/off, climate changes, etc.), as well as setting security mode for a house, viewing security camera pictures, and triggering "speak to person inside the house."
2. Blu-Ray functionality is still nacent. We have to rip the disk to the core, and it can be played throughout the house. No menus yet, just movie currently.
3. We release incremental updates via the update mechanism, they are downloaded when available, and you are asked if you wish to apply them. Distribution upgrades currently must be done by downloading a new DVD. At which point, you are asked if you want to keep /home, settings, or both.
4. Currently the 8800 is not supported by the copy of NVIDIA's driver that we bundle. But you can download the driver and upgrade it. instructions are in the wiki. As far as hardware decoding, NVIDIA has told the Linux community repeatedly that they WILL NOT release a driver with functionality like PureVideo HD, this has happened despite repeated attempts at trying to convince them to change their position.
5. right now, we do not have a mobile page for doing guide work. We do expose mythweb for normal browsers though.
We are trying to solve a much larger problem domain than Windows MCE. As such, we are fleshing out many subsystems at once, much more than just media. The system will eventually come to encompass what you are looking for, and much more, but we have to write it.