In my exeperience calculated fields are totally useless and I have never found a use for them. I generally use a custom field and do any calculations using functions as an update action on rules and such custom fields are available in filters and indeed as conditions for rules.
we use a small number of calculated fields which are visable in certian views. The only way we can really use the data in the calculated fields to find or isolate data is to export the view with the calculated field and import the data into e.g. Excel / Access etc. from which we can then run what ever reports we have set up. Thi sincluded filering.
The data is really only as up to date as the time that we ran the report however we can live with this.
You said: "...isolate data is export the view with calculated fields and import the data into e.g. Excel / Access etc. from which...". How do you obtain to configurate the datas of Calculated fields when these informations are exported for the Excel? Because when I export the informations from Calculated fields for Excel, these datas arent configured correctly.
this is why we only use a small numer of calculcated fields even in the exports. generally we have been able to change the format of the cells in the excel sheet to something that will allow the data to be presented correctly.
Right click the cells and choose format and from there find the appropiate format to use. Custom generally helps.
Failing this I am not sure what else you can do to display the data.