Where you are using roaming profiles this would mean that the cache may be removed when it needn't be - not a big issue where your users always use the same computer, but potentially a problem for example in the Citrix environment where your user may rarely log on to the same machine twice in a row.

Including the machine name in the registry path would avoid this problem, but would bloat your HKCU hive as each machine you log onto would create an independant cache.