AT150 started at $39.99 ($44.98 with local ABC, CBS, NBC, Fox.  PBS $1 more).  
It is now $44.99 ($49.99 with locals incuding all or most locas in the area)
When AT150 came out it did not have the following channels:
VH1 Classic
Great American Country
Oddysey (Now Hallmark)
National Geographic Channel
Style
Fox Sports World (English)
Boomerang (the channel itself launched after AT150's introduction)
Wisdom
CNBC World
RealityTV
Gol TV
Nick GAS
Channels that were not on AT100 at the time (nor AT150)
Much Music (Fuse)
Lifetime Movie Network
Noggin / The N
SoapNet
(won't count Discovery Health because it really replaced Discovery People it just took it a few months)
Channels that were not part of AT50 (nor AT150)  Short list:
TV Games
15+ public interest channels
---Shall I add up the shopping channels added....No. 
 
Just putting things in perspective.  Yes most of these additions came quickly after the formation of AT150.  However, people seem to forget just how much has been added.
BTW, the above is from memory.  I've been keeping track of channel additions and changes in general since 8/1/00.  So you can check out all the additions from then for yourselves.  AT150 was made available in May 2000.
http://ekb.dbstalk.com/247-1 Changes from 8/1/00-12/31/01
http://ekb.dbstalk.com/247-2 Changes from 2002
http://ekb.dbstalk.com/247-3 Changes from 2003
http://ekb.dbstalk.com/247    Changes from 2004
See ya
Tony