Retracting my comments
I have recently performed a hard reset and re-installed all my apps including Pocket Informant 2005. All the problems I was having with PI2005 seem to have vanished. It runs as quick as ever and I am once again very impressed with this PIM.
My above comments are partially retracted regarding the sluggish behaviour of the graphics where it seems to have been caused by something else that was there before the reset.
I do still believe however that you cannot really improve this app any more... It is perfect really. WebIS are going to find it hard to come up with new stuff.