Personally, the whole trade in thing does not seem to applicable to me if you are upgrading to HD. For me, the 600 or so dollars I could save by trading in doesn't make a bit of difference when looking at the $10,000 minimum that it takes to get a small HD 1 setup (thats not including the computer). I know for certain that I could not live with 32 track limitations. I really like over tracking and cutting things in the mixdown stage. I do like Pro Tools as a software platform, but even with M-Audio as an option, I would still feel locked in. For one, I do everything I can to avoid M-Audio, and you still have to buy the software if you do the M Audio route. I have to admit though, the fact that they do lock you into certain hardware may be a drawback for me, but it is also an advantage for some. That is one of the ways they can guarantee more reliability, by taking away options. As far as transfering a session to a larger studio, I wouldn't care about anything except the time alignment of tracks. If I were bringing a project to another studio for another engineer to work on, I would want them to start from scratch so they can do their thing (which is why I would be bringing it to them to begin with). I would never give another engineer material to work on and tell them "here you go, I did half the mix, you finish".
In the end however, Pro Tools is still an industry standard. Not necessarily because it is the best, but more because it is the most familiar. 5 years ago TDM systems were in a very select group of capable software solutions. Now there are many options and that gap has narrowed down to a very slim margin. HD processing is really about the only advantage that digidesign still has as far as capability goes, but LE does not include any of the stuff that makes an HD rig so powerful. I have however been considering adding an HD1 sytem in my studio just because I am sick of the first question from clients always being do you have Pro Tools? At least then I could say yes and when they get here use Cubase SX anyways.
Personally, knowing the limitations is probably the most important factor. If you think there is any chance you may have a problem with the limitations, I would not consider Pro Tools as an option. I do not think that Digidesign is going to change the LE software limitations or offer LE compatible hardware with any more I/O than the Digi 002 and 002R. If they did they could easily undercut their own (and far more profitable) HD sales. The reason I don't reccomend Pro Tools LE to anyone who may need more than it offers is because when they reach that point they will be forced to learn a whole new software. If you see that you may want more, just pick a solution right away that can grow with your needs. If someone asks me for advice and is willing to invest in HD, thats a whole new story. I would reccomend HD to that person. I do think it is overpriced, but so are Neumann U87's. That does not make them any less of a mic though, and they offer a name and reputation that will more than likely help to bring in enough business to offset its slanted price.
As far as the actual question at hand, there is no appreciable sound difference between an Mbox and a 002. If it is true that Digi has changed the preamp in
the Mbox2, than there is a really good chance that
the Mbox2 will actually sound better than a Digi 002x. Digidesign is known for their software. The digidesign LE compatible hardware is certainly not known for its converters and preamps.