Hi Svennn,
In their day, Forntier Miniatures were "OK". They weren't horrible, but certainly not outstanding. The one big advantage they had when they first came on the market was that they covered some periods that were different than the run of the mill gaming periods.
When doing a size comparison to Foundry figures you will find them to be on the small side. If comparing them to Copplestone or Perry figures they will appear down right tiny. They are closer in size and build to old Minifigs.
They have a tendency to have a somewhat "bug eyed" appearance to them.
If fleshing out some LARGE units and if you can get them at a cheap price you might be satisfied. But, don't expect outstanding quality.
Hope that helps.