Feco[feko]

You mean FEKO?

I've tried and only what can say it's unfriendly compared to other EM simulator. I also appreciate reports about accuracy.
Eirp

If you want to know how is easy to work in other EM simulators like Zeland, MWO, Genesys, CST .... than you would to try FEKO.

Build geometrical structures is very hard, like in 4NEC2(Settings>NEC-2 editor and you'll get very usefull editor similar like in Feko), but 4Nec2 is free.

Feko is MOM tool and because is very accurate and fast.

Edited.

I also want to know the accuracy in feko when compare with other EM SIMULATORlike ie3d,hfssand CST.

Femap have bad user interface too.
CST is the best and with Femap you can easy to import in Feko from CST, but new problem will come, problem with optimization because we can not to change dimensions of imported files(*.neu).

Is it possible to import Zeland structures or zeland exported files like dxf, GDSII or CIF?

Feko is more general than IE3D, ensemble, MWO's Emsight. For example, it has spherical green's function, it can combine mom with high frequency asymptotic techniques, etc. Many people don't like the interface because it is text-oriented and can't display the geometry of the problem in real time. On the other hand, this gives you more control over the model and the simulation, and I like this a lot.

For the few problems (filters, conformal antenna, etc.) that I have tested against IE3D or HFSS, the agreement is satisfactory.

Regarding Femap, if you like Windows interface, then you would find Femap better than many other meshers (GiD, Gridgen, etc.)

i did a rectangular patch antenna(infinite ground and infinte substrate) with a coaxial feed and the results between FEKO and IE3D were very similar.
I did have problems about defing the port but once you know how to use the control cards i think its very straight forward.

I agree you all, but i want to say feko is very useful when you compute very large models.