Are there any disadvantages about using eggs through easy-install compared to the "traditional" packages/modules/libs?

One (potential) disadvantage is that eggs are zipped by default unless zip_safe=False is set in their setup() function in setup.py. If an egg is zipped, you can't get at the files in it (without unzipping it, obviously). If the module itself uses non-source files (such as templates) it will probably specify zip_safe=False, but another consequence is that you cannot effectively step into zipped modules using pdb, the Python debugger. That is, you can, but you won't be able to see the source or navigate properly.