I'd like to add another biased opinion.

And my bias even has some professional experience behind it!
I used to be a Mac tech at MacMall years ago. After that I went independent and did on site computer repair for both Mac and Windows systems. I've been good at IBM clone computers for 16 or so years? now. I was good at this back when you had to free up conventional memory in DOS to make games work.
The short answer is I love Macs and would only consider them for my primary work system. At this point I like Vista too. Yeah, a Mac lover who likes Vista. But OS X is still more stable and the overall "Mac experience" is much more cohesive and stable. Macs are almost overdone when it comes to how they are designed and this includes the hardware as well as the software. And this shows in the daily experience.
Also, as much as I like Vista, it still has some issues that have plagued Windows since the beginning. One of them is the fact that Windows needs to be reinstalled every few years or it gets slower and slower and slooooower. I'm not totally sure why this is but my theory is it has to do with how Windows stores information about itself and it's installed software (the registry). Regardless of the reason, that is a reality with Windows systems. On the other hand, I have a first generation Mac Mini which I use as a server at home. That little system is rather old for a computer (5 years?) yet it continues to plug away and doesn't slow down over time.
My latest system is a Macbook (though it was supposed to have been a 17' Macbook Pro... lost a client and 50% of my income... ARG!). Considering it's Apple's entry level laptop, it performs quite well. And the default memory it comes with is enough even for running Windows at the same time as OS X for those moments when I need a Windows app.
Regarding purchasing extra memory, Apple generally overcharges for memory upgrades. I recommend going here, they have a very good reputation:
http://www.crucial.com/
For running Windows I am aware of three options. Installing it on your Mac using Bootcamp (you will be able to restart your computer in Windows) which is free except for a Windows license. Or you can purchase software which allows you to run Windows at the same time as OS X (still need to purchase a Windows license). I've used both of these and prefer VMWare's Fusion (though they are both good)
VMWare Fusion:
http://www.vmware.com/products/fusion/
Parallels:
http://www.parallels.com/
Also, before you buy a Mac, it's highly recommended you check where Apple is in their release cycle for your intended product. You can do that (though the cycle is educated rumor rather than actual fact) here:
http://buyersguide.macrumors.com/
Buying something and then having a much better version come out for the same price a couple weeks later is very frustrating (I did that with my iPod, ARG!)
If you compare dollar to dollar up front the Mac will tend to be more expensive (last I read that isn't the case with Mac Pros but that can change). But the TOC (total cost of ownership) is MUCH LOWER when you consider stability, lifetime of the product (or the need to reformat every 2 years with Windows) and overall experience. For your usage you won't even need to purchase anything (web browsing, TT and posting in forums). Although every Windows app doesn't exist on the Mac many of them (or some alternative) do. And for that ONE program you need, you can still run Windows on the Mac. The main hole is video games which is why I still purchase Windows desktop systems as well as Macs. But if TT is your video game there is no issue there, it works equally well on both systems.
If you have any specific software concerns, let me know, I tend to keep up on software that works on both platforms so I can use the same thing everywhere.
And when you're feeling really insane you need to try Linux!
My only problem is, you can't right click in Windows. In the Mac OS it's Ctrl-Click for right click. It's something they haven't figured out, but they say with an external mouse it can be done. I rarely use the Windows side much, but I have it if I need it.
Funny I never noticed that, I always use an external mouse unless I'm out with my laptop which is rare. I may be acting like an annoying Mac fanboy but.... that issue should be a lack of a proper driver on the Windows side so I think we should blame Microsoft for the lacking right-click in Windows.
Wow! That is a lot of money for a laptop. LOL! I was looking at it and I would upgrade the memory and all that stuff. It would really get up there in price. I don't know if I want to spend that much since we just got this one recently. Decisions, decisions. Of course if I win big in AC Ill buy two. LOL!
I already mentioned the RAM, for the hard drive upgrades, Apple's prices aren't unreasonable and the 7200 RPM drives tend to be worth the performance increase. From what I've read solid state drives are overpriced for what you get from Apple or anyone else. That should change as they get more mainstream which will force the price down. For upgrading the processor, I always discourage going for the fastest processor, computer companies always charge a premium which is rarely worth the upgrade from the next lowest option.
Hope that helps.
Josh