How many devices can connect to an Agere Broadband Gateway 2000,
assuming sufficient IP availability? If I set up the DHCPd to hand out
255 IPs, can I use 255 laptops with my Agere Broadband Gateway
simultaneously?

Good question. The Agere documentation is sadly lacking.

The short answer is no, the thoretical maximum is 63 connections (from
the 802.11 standard), and the real world limitations push that number
way down, depending on the amount of network traffic.

One answer can be found in an article written by James McPherson

http://libra.unitbv.ro/internet/network_speed.htm

"In a wired world, every device has its own link to the hub. However,
the wireless world has to share signaling channels if there are more
clients than channels. (The 802.11b standard for DSSS is to divide the
2.4-GHz band into fourteen 22-MHz channels; the U.S. standard uses 11
channels; in Europe and Asia, the standard uses 13 channels.) Packet
collision will occur on a wireless network in the same way it would on
a wired network up to the point that the number of clients equals the
number of channels. Once that number is exceeded, packet collision at
the hub level ramps rapidly as the data signals become mixed and
mangled."

Also, from the same article

"The big difference is that in the case of 802.11b wireless, the
specification allows up to 63 clients per base station"

This is a common issue with network admins, as you can see from the
exchange at

http://csl.cse.ucsc.edu/pipermail/aironet/2001-August.txt

"I wanted to find the true number of clients it can associate at one
time. I found that the Linksys WAP11, for example, can associate only
63 clients."

The data sheet (PDF) for the BG-2000 shows that it is indeed an
802.11b standards device with 11 channels.

ftp://ftp.orinocowireless.com/pub/docs/ORINOCO/BROCHURES/A4/BG-2000_A4.pdf

ZDnet reviews the gateway as being a good performer, but offering
sub-standard support.

http://www.zdnet.com/supercenter/stories/review/0,12070,561389,00.html

The IEEE standards are available online at:

http://standards.ieee.org/catalog/olis/index.html

Google search terms:
"number of channels" "number of clients"
802.11
BG-2000

I hope this fully answers your question, 

Thank you for using Google answers.

Putting theory aside, the correct answer is 10. This number comes from
correspondence with Nicholas S. Mantz, a member of "ORiNOCO’s"
Pre-Sales Team. The body of his email back to me is as follows:

"Thank you for your interest in our products. In response to your
question,
the BG-2000 can support up to 10 concurrent users.


Regards,

"ORiNOCO" Pre-Sales Team

Agere Systems"