I've also heard this described as "lumpy" performance!
This can be seen in Office versions 2007, 2010 and the latest 2013 (including Office 365 click to run) with all updates applied for both Office and Windows.
While this can be caused by a number of factors, such as insufficient vCPU/vRAM in the guest OS or resource contention at the host level, it could also be due to a setting within Office to disable hardware acceleration.
The key is to understand exactly what is happening and verify it is not "latency" on the LAN/WAN connection and that only Office applications appear to be affected and randomly freeze, while other applications do not hang.
1. Within one of the Office applications exhibiting the issue, go to File --; Options
2. Go to Advanced --; Display
3. Tick "Disable hardware graphics acceleration" and Click "Ok".
Note: This setting applies to all applications (i.e. If you set it in Word, Excel will pick up the setting at next launch).
4. Close all Office applications and then open the application which exhibits the problem the most and confirm this has resolved the issue.
Note: If this has not resolved the issue the problem may be due to resource contention either in the guest or host.
If this is the cause, user feedback after 5-10 minutes us usually along the lines of "wow what did you do" and "that's a million times better!" or "it's like a local desktop", provided everything else in the VDI environment is optimized and working correctly.
5. To deploy this fix to all users, this setting can be made in a group policy object (GPO) to ensure all VDI users get this optimization.
User Configuration -; Administrative Templates -> Microsoft Office 2013 --;
Miscellaneous -; Do not use hardware graphics acceleration