Basically, I got more done when using a straight PC at a previous office than a Mac [with bootcamp]. This is the bottom line. It is a constant frustration.
I'd have understood if you'd not mentioned bootcamp there. In bootcamp, your Mac is 100% a standard PC. I'm not sure what you can do on a 'regular' PC that you can't on the Mac under Bootcamp.
Basically if the software you use day to day is not available, using a mac becomes a nightmare no matter how you defend it.
When working, you obviously need access to all files, email, internet + software. It does not make sense to switch about, which is my problem.
I'm a network admin and .NET developer. Naturally, my work-supplied laptop is a Dell. However, it's not a flat-out rule that even then it's not possible to be productive with the Mac. Visual Studio 2005 runs excellently in Parallels. I have plenty of scope for making use of both environments simultaneously. I'll often draft program execution flows using OmniGraffle in OS X which I save as a PC-friendly format and drag into Visual Studio for inclusion in the documentation. I prefer Keynote to Powerpoint, so I do the same there (and often get complements on the quality of my presentations - "Wow - how did you get Powerpoint to do those effects!"). OS X can connect into my work's VPN, which allows my Parallels windows environment to log into our domain, meaning all my work-related documents are kept in my domain profile and synchronised between Parallels on my Mac and my work PC.
Email's easily accessible via Outlook Web Access. Ask if your company's Exchange server has OWA enabled, then simply point Safari to the proper address. OWA's very full-featured and quick (sometimes I prefer it to my PC's Outlook installation, even on the PC!).
BTW I sorted a network with XP between 3 Macs in bootcamp in about 10 minutes! It took me a few hours and stress to get networking in OSX as I wanted it, and then all the machines wouldn't shut down properly and everything ran slowly - so please don't suggest that XP networking is bad.
Likewise, please don't suggest that because you've seen problems with OS X's networking that OS X's networking is inherently bad. My 3 Macs network flawlessly in OS X, Parallels environments and Bootcamp, using both Windows SMB networking and Apple AFP. Also, OS X perfectly happy browsing network shares in the office from home via VPN.
[edit: just to comment on a few of your other points]
2. All the software I really need runs on PC only.
Well, there's a couple of ways of looking at this. It's true that there are certain applications which have no OS X equivalent, or the equivalent is a bit odd. Outlook versus Office: Mac's Entourage is a good example. On that particular issue, I chose to work around as best I could (using Outlook Web Access) and ensure I had access to the 'real deal' should it be necessary (Parallels).
But this situation needn't blind you to the range of applications on the Mac which have no real equivalent on the PC, either for quality or for ease of use. I'll never touch Powerpoint again after using Keynote and Windows cannot give me Keynote. I much prefer OmniGraffle to Visio and would take OmniOutliner over OneNote. OmniPlan is shaping up to be something great too. Heaven forbid, but I also prefer the Mac versions of Word and Excel to their Windows counterparts!
The Mac and its software is now an integral part of how I work - small things like the ability to convert anything, anywhere to PDF which a click of a button is invaluable and has made my Adobe Acrobat-using colleagues at work green with envy. Bear in mind that the cost of 2 licences of Acrobat Professional would buy a MacBook outright! Then there's the big things - the way I can script almost any and all applications within minutes to perform frequent tasks. Build workflows with Automator that'll process data in multiple stages quicker than anything I could set up on the PC (Folder Actions are absolutely invaluable - I actually ended up spending a month developing a 'Folder Actions Service' for windows to emulate this functionality on one of our servers!).
If you're willing to spend some time looking at what the Mac can do for you, you'll see the value in it. OS X's applications and features have (for me) built into something of a supporting framework for the few must-have apps I run in Windows via Bootcamp. The Windows apps I need essentially sit in their own sandbox, with OS X humming along for everything else.
3. Outlook for PC is great and compatible with the rest of the world.
Basically, the 'groupware' features of Outlook are compatible with the groupware features of... well, Outlook. Even its HTML mail format is a little odd and only really displays perfectly in other copies of Outlook. I've never had any problems whatsoever with Apple Mail. The font may look slightly different, but I suppose it depends on you if you consider that a 'problem' or simply 'how it is', thanks to Microsoft's design of Outlook.
4. Is just as fast, and crashes the same amount of times, no matter what people say.
That's a pesonal data-point. I can provide you with a data-point from my experience that says completely the opposite.
5. Vista is basically OSX visually, which was my main draw.
.... and there's the problem. If eye-candy is what drew you to OS X, then is there perhaps a possibility that you're overlooking the actual abilities and features of OS X, prefering that it behave 'just like Windows'?
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, don't add anything.