I'm a long time Mac user, I've never bought anything but Macs. But because I won't own an all in one either I too am considering a Windows machine as an alternative.
Apple gained switchers because of the mini. But now, because the an all in one is the only mid range computer Apple makes it looks like the iMac is starting to cause switchers in the other direction.
Yep, Mini had a major role in attracting switchers, particularly before Bootcamp. However, since Bootcamp, its original main purpose has become increasingly superfluous, so little surprise here that last year's redesigned Mini wasn't only over-priced (certainly in UK), but there's only 1 model (the other being a server), suggesting that Apple won't spend much more time on advancing it in future.
Probably some truth in what folk say about SJ/Apple much preferring to see it canned sooner than later, as profit margins for the Mini remain much lower than for other Macs, with most Mini-owners probably also using non-Apple monitors.
Frankly, with my said personal experiences with the iMac & views on glossy screens, I'm not surprised that other people are either considering, or are actually switching to W7, if only to open themselves to greater choices in hardware.
That said, it's not an easy decision (for me at least). Probably as with you, since buying my 1st Mac in 2005 there are many things I've learnt to do on Mac that are automatic, with little conscious thought involved. That's a major plus for increasing ones work-rate. Whether with W7 or Linux, it'll take time to re-adapt to attaining the same level of fluidity.
Whatever I decide in coming weeks, as I said on Macworld UK recently: "I still have a high regard for Macs (& my ageing iBook continues to be very reliable), but I don't really believe that Macs are any better or worse than similarly-priced Samsungs, Sonys, Dells, etc. For me, what gives Macs the cutting edge has always been the quality of their software, esp pre-W7 era."
Since W7, from what I've read many times on various forums including Mac, I get the impression the advantages of OS X are no longer as clear-cut. So without discounting buying a new Mini, I'd be cheating myself to totally ignore other options. - All the best whatever you decide to get!