Omega's drivers ARE the ATI Catalyst drivers. Omega does not write drivers.
The Omega's are simply re-bundled ATI Catalyst drivers with different default settings (same that can be performed with 3rd party tools, ATI Tray Tools or CCC) and more fool-proof/broken-system friendly INF/installation procedure.
The best thing about Omega's drivers are people with inherently broken systems or convoluted registry have better results wedging them into their systems. The real answer to get flawless driver installation is to clean up your system, delete old/obsolete registry entries, and use tools like Driver Cleaner Pro.
You do NOT need .NET installed to run the Catalyst drivers- this is only needed if you wish to use the Catalyst Control Center (for adjusting settings). You can either download the older Control Panel from a prior Catalyst driver link, or just uncheck Catalyst Control Center and use a 3rd party tool such as ATI Tray Tools or RivaTuner. I still recommend CCC for users of X1800->X1900 cards as the CCC's Overdrive is currently the best, most stable method of getting the correct core/mem speeds in games.