Since you say you liked your mac solution, get a mac notebook if you don't have one already. As long as you don't hook it to the corporate network, there shouldn't be any objections. The GTD apps that fit my needs best are on the Mac, and life is just too short for inferior tools.

iGTD is worth a look if you haven't done so already. However, I've given up on web apps for two reasons. Other than iGTD, none of the solutions are close to being as good as what I already have on the Mac (I use kGTD and Devon Think), and I don't trust that the developer will be there a year from now . . . never mind 10 years form now (this certainly applies to iGTD).

I have made numerous compromises - including not being able to take everything with me wherever I go. I accept that many projects will live in Microsoft Project, and I accept that some common work flows will never make it to my Mac (stuff from our HelpDesk and procurement systems). Of course, these inputs would be just as untouchable to a web app as well; and, to a certain extent, would even be outside a PC-based GTD solution.

A consequence of my approach is that there is a great deal more cutting & pasting than would be the case if I would have accepted a GTDed Outlook solution. Again, I think it is worth the extra effort though I'm sure some would disagree.