The downsides of using portables -
Hard drive speed limits track count - most laptop drives are only 4500 RPM. Some offer 5400 RPM, but that's the fastest I've seen.
Internal sound cards generally suck.
Pointing devices generally suck. (External mouse helps)
Multiple sound cards are difficult to set up. (firewire cards can be daisychained with proper drivers)
Large amounts of ram are more expensive. (Get all you think you'll need when you buy; laptops are not known for ease of upgrade)
Dual video is rare enough that I've not seen it in any laptop yet.
The upside is portability. This is sometimes worth the downsides, especially because:
Hard drives speed can be overcome by using a fast interface external drive. This would be either a PCMCIA SCSI card with an external SCSI drive, or a Firewire drive. These are available in at least 7200 RPM versions. USB2 is fast, but I've seen several reports of incompatibility with P4's - I would stay away from that option until Intel learns how to mate the P4 with USB.
External sound "cards" - There is at least one high quality PCMCIA one, I believe it's called the "pocket" something or other - two channels of XLR if I remember correctly. It is not cheap. There are more and more Firewire audio interfaces every day. At least one includes preamps with phantom power (MOTU 896)
For the above reasons, If I were to buy a laptop specifically for audio I would not even look at one without a Firewire interface.
The other possible problem that I might expect to see would be using a Firewire drive AND a Firewire audio interface. If you are recording 8 tracks at once AND accessing a Firewire drive to record them, you might run into a bandwidth limitation, but I doubt it. Firewire has a bandwidth maximum of 50 MB per second. 100 tracks of 24/96 audio takes 27+ MB per second, so it should be no sweat to transfer 8 tracks to disk, 24 tracks from disk, and 8 tracks to the computer from the sound card all at the same time, even allowing for other overhead.
In the studio, if you want less noise you would have to remote the keyboard, monitor and mouse and put the laptop elsewhere. Desktop machines generally make more noise, so the only difference here would be the method of extending the control/viewing.
Those are the main things I would consider, there are probably others I've missed... Steve
