I have two - the iBook in my sig, and a Dell Inspiron. I already had the Inspiron, and then 7 months ago I bought the iBook. I thought I'd never use the Dell again, and indeed for some 4 months I didn't. I was thinking of donating it to a friend, but then reality hit. There are several programs that I have to run, which are windows only - and recently I've been made acutely aware of that. I was pretty infatuated with the whole mac experience, and I grew overconfident about not needing windows, but now I'm more balanced, and I realize that you can't get emotional about it, just use the tool that you need.
It is with great shock that I realized that the world of mac software is tiny, tiny, tiny. For example, once I finished editing my 140 minute video in FCP (which was a great experience - love FCP 4.5, love my iBook), I wanted to output it to a DVD. That's when the pain started. I don't have FCS, and so no DVDSP, and don't want to shell out $200 to get it (in an upgrade, otherwise it's $500, if you can even get it... it's been folded into FCS 5). Well, I couldn't believe it, but it looks like DVDSP is the ONLY app that will do a 140 minute DVD authoring! iDVD is limited to 2x60 or 120 minutes. Wow. There's some controversy as to whether you can do it in Toast 7 with any decent quality after importing from FCP, but that's also $$$. Meanwhile, google for windows DVD authoring software, and you've got a seemingly ENDLESS choice at all kinds of price-points and huge numbers absolutely FREE! Very humbling. So, I'll have to actually finish my work on a PC
... and this is in an area that Apple is supposed to be strong in - creative, multimedia etc. Imagine what happens when you look into more niche markets.
And I've had the same experience in more areas (for example encryption software - vastly more and way better software available for widows compared to mac), and by now, I've come to accept that OS X will always be a poor cousin in the software world. Therefore, having access to windows is an absolute necessity for vast numbers of users. Hence my Dell laptop will not be abandoned anytime soon. Then again, once I buy into the intel macs, there's always boot camp, so I may no longer have to keep a windows machine around
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