On a CentOS 4.1 machine yum 2.2 takes 20-30 seconds everytime I use it like this:

#yum update xchat
Setting up Update Process
Setting up Repos
dag                       100% |=========================| 1.1 kB    00:00     
update                    100% |=========================|  951 B    00:00     
base                      100% |=========================| 1.1 kB    00:00     
contrib                   100% |=========================|  951 B    00:00     
addons                    100% |=========================|  951 B    00:00     
extras                    100% |=========================| 1.1 kB    00:00     
Reading repository metadata in from local files
dag       : ################################################## 2669/2669
update    : ################################################## 75/75
base      : ################################################## 1406/1406
extras    : ################################################## 30/30
Could not find update match for xchat
No Packages marked for Update/Obsoletion
# yum --version
2.2.2

On a RHEL 3.3AS machine yum takes mere seconds like this:

# yum update xchat
Gathering header information file(s) from server(s)
Server: RedHat Enterprise Linux Base RPMs 3AS/i386
Finding updated packages
Downloading needed headers
No Packages Available for Update
No actions to take
# yum --version
2.0.5