Nothing, it's a turn of phrase. I'm saying that the amount of effort Microsoft puts into some of their WPF-based applications is questionable. That I don't trust them to maintain high standards of quality across the board consistently.
Visual Studio 2010's GUI is WPF, but that doesn't make it perfect. I, myself, have many issues with it (menus are laggy on my 6-month old laptop, for example). It's not a deal-killing issue (no, the inherently broken Help system was) but just something that irks me. And when a product has too many things that irk me, it damages my impression of the product and makes me want to look for a competitor that 'feels' better to me.
For example, I skipped Office 2007 because I found the UI too cluttered, the help system lacking (not saying 2003's is any better, however), the hard-coded colour schemes inflexible, some parts laggy, and Access (which I used a lot at the time) had a really degraded user experience (the home page is full of adverts, wtf). I was tempted to overlook Office 2010 too, but I'm pleased they fixed it up, but had Office 2007 had a better qualiatative experience I'd have certainly gone with it.
Other examples of 'tiny things adding up to make me abandon-ship' include:
Moving from WMP9 to WMP10, then realising Winamp is what I'm looking for
Windows Mobile 5.x, then seeing that Windows Mobile 6.0 was awful ('glass' gradients do not work on mobile 16-bit displays) and WM6.1 and 6.5 were just mere facades over decades-old platforms, then discovering iOS
It's not all Microsoft stuff: The MySQL Workbench toolkit is (in my experience) not the most user-friendly or simplest of GUIs for MySQL Server. I'm sticking with MySQL Administrator and MySQL Query Browser, a 2-part toolset (similar to MSSQL2000's Enterprise Manager and Query Analyser tools).
Another third-party example is Nero. I started using it in early 2002 when I got my first CD burner. It was a small and light CD burner and image-making software. I started to notice things going wrong around 2006 when it started including "Nero Scout" (Yet Another desktop search engine) and other bundleware that had absolutely nothing to do with CD burning. I also noticed they removed the ability to create ISO images (only their bastardised "NRG" format). After setup gave my computer a number of service processes that served absolutely zero purpose I found ImgBurn which does everything Nero does, and a lot more besides, all within a tiny binary. It also looks good on Windows thanks to judicious use of icon art and pulls no stupid patronising UI tricks like Nero did.
and i will say that i have a few apps that seem to do ok.
not masterpices of art or design but they look ok and work well on normal hardware. I think you just have not seen many apps. some like mine are customer for a given customer and not in mass market. but they should not make any one wish to remove anyones eyes (mine or the users)
AutoCAD 2011. I used it for a minor design thing I was working on mid last year (granted, I was using it as a glorified file format converter, but still...). The main program is native as you'd expect, but their ribbon UI was implemented as a hosted WPF control. It was horrendous: incredibly slow and laggy, but also very, very ugly (even when used on Windows Vista/7).
Part of what kills WPF for me is the lack of support for alternative visual styles, even official Microsoft styles, and instead gives you a (deliberately?) ugly Windows 2000-style look. I know it's partly due to the vector-based UI in WPF, but the Visual Style API was designed so it could be used from DPI-independent applications and services. It is possible to build a WPF skin that pulls artwork from Visual Styles, and I'm disappointed Microsoft didn't invest in this. It also means that there's going to be headaches in WPF applications 5 years from now when Microsoft ditches 'Aero' as the main Windows style and all these WPF apps are going to look out of place.