Increasing Speed
The most common thing to speed up is in the performance of Add2Exchange is the Performance tab in the Add2Exchange Console Services Utility.  
http://guides.diditbetter.com/a2e-enterprise/application_performance.htm?zoom_highlightsub=performance

It is probably set to 6, the default, but be careful if you increase it too far and so fast (to the left), make sure you are not hitting 100% cpu utilization  during sync - ever.  When changing this item, close the Console and start the service and monitor the taskmanager for 10 minutes or so and see that it stays under 75% or peaks infrequently.  If Add2Exchange is installed alone on a utility server, and not on the Exchange Server, for example,  you can ratchet it up until the time it takes is the best you can accomplish, given your infrastructure and layout. 

There can also be some other systemic things which are slowing things down which could be optimized.

There is a brief section in the guide which deals with this, at the following link.
http://www.diditbetter.com/manuals/Add2Exchange/Add2Exchange%20Enterprise%20Guide/index.html?post_installation_instructions.htm

NOTE: There was a release on 03/19/2013 that addressed a speed issue with GAL Sync.  Please update to the latest version, using these procedures.

Some Other Helpful Speed Increases:

See this link 

Antivirus Acive File Scanning Exclusions and moving the temporary "MMP files" out of c:\Windows\Temp"  to a new directory so we can exclude the directory from scanning:

Big TIP: MS puts the temporary Exchange profile files needed for proper operation in the c:\windows\temp directory. We would want to exclude these thousands of temporary files from active file scanning to.  It is probably a bad idea to exclude this directory (c:\windows\temp) common virus hole from active virus scanning so it is probably best to follow this MS Tip and move the location for the temp files MMP files entirely.  It is our opinion that it is  best to move the location and not just to exclude the file type mmp, since that would trigger a deeper comparison by the antivirus software rather than excluding the whole new directory we create which will be accessible by all programs, and then make sure the new location would be excluded from Antivirus scanning.
http://support.diditbetter.com/kb/A2E_218.aspx

I suggest making a directory (on the local box) named something like "c:\Windows\MMP"
and using the link above to move Microsoft CDO Temporary files, and then be sure to exclude from Antivirus Active File scanning along with those above. 

TIP: You should make a new directory, and not just exclude the c:\Windows\Temp directory.

These are the appropriate directories to exclude from Active File Scanning from which the Add2Exchange software uses to operate. Make sure to exclude these dirs

(path is for a default 32 bit system install)
C:\Program Files\OpenDoor Software® and all subdirectories
C:\Program Files\Microsoft SQL Server   and all subdirectories
If Exchange 2003, exclude C:\Program Files\Exchsvr\bin (and transaction logs dir) and all subdirectories
If Exchange 2007 or 2010, exclude C:\Program Files\ExchangeMapi

and if yours is a 64 bit system, find some of these under \(x86) directories

Data Execution Prevention 
To make your system completely aware of its function as a replication server, check to make sure that Data Execution Prevention (DEP) is either off  except for essential Windows Programs or if on, you SHOULD exclude these files. 

Right click, my computer, properties, Advanced, DEP. 
If on, exclude these files
(Default path on 32 bit system)

C:\Program Files\OpenDoor Software®\Add2Exchange\Console\
Add2Exchange Console.exe
A2E Director.exe
A2ESP.exe
Add2Exchange Service.exe (if possible on your box)
and if Add2Exchange Enterprise these additional
A2ERelMgrPgm.exe
A2EGALMgrPgm.exe

Tips for decreasing the size of the folder to sync in Add2Exchange and Add2Outlook

If the source folder is a calendar folder, another consideration for faster sync speeds is the number of OLDER items in the folder.  Although our sync programs only sync changes, if the number of items in the folder are large, it takes more time to investigate the changes.  So one component of the speed at which syncing occurs is dependent on how many items are in the source folder.  One way to increase sync times is to archive older appointments.  The more older unchanged items in the folder, the longer it takes to replicate.  

TIP: Use the Outlook archiving capability.

Add2Outlook Only

Sync times depend on your connection to the internet, the speed, capacity and load of the sync machine, and of course the back end connection of your exchange server or host provider.  Occasionally since we are syncing data, host providers may need to allow for a "non throttled" service account, check with your host provider for more details.

At one point the systems were recommended to be in online mode because some hosters will not allow for granular limiting of mailbox access.  If the system was in cached mode, it would cache entire mailboxes, which is unnecessary overhead.  This may not be necessary with Exchange 2010 installations anymore.  If speed is slow or disconnects occur frequently, change to cached mode and sync.  If relationships go into alert, recover them from the Add2Outlook Recover Relationships option.  TIP: Be VERY careful and pick the correct folders if prompted and necessary.

These tips should speed things up a bit - please give us some feedback on your experience.