Personally as a UK Taxpayer I don't really care whether the desktop PCs and downing street or Whitehall run Windows , Linux or Mac they could run Haiku for all I care.
What I am more concerned about as more government functions can be interfaced with online is whether this will be done using the most standard and open data formats etc possible.
If I need to buy a specific piece of proprietary software to submit my tax information online or if all applications for public sector jobs are distributed in the latest MS Word format that I can't open without buying a new version of Windows and office then that is something I at least potentially care about.