I use PT LE at home and at work, and have used the TDM systems on a few projects.
LE (which I use on a Windows XP machine with the Digi002) is stable and very easy to use. Like all native systems, the plugin count and track count depends on your computer hardware, but I get plenty of functionality out of it for my purposes. LE now has a 32 track limit for audio, but things like effects returns and internal busses are not included in that count.
The TDM systems that I have used are head and shoulders over LE in terms of signal processing, but for my purposes that seems to be the only difference. There are better plugs availible for TDM, but I can't afford them anyway. Also, TDM works on its own hardware so your computer specs almost don't matter. The TDM systems have many other pro-level features (big mixing & control consoles, video sync, etc.) but you PAY for them. If you aren't making money with it (i.e doing pro work) it would be hard to justify the expense.
On that note, PT LE sessions do transfer seamlessly over to TDM systems. You can lay your tracks at home, burn your session to a CD, and take to a pro studio with a TDM system for mixing. I'd imagine that not too many people will actually use that capability, but I know several people with TDM systems so I do. Worth its weight in gold if you need to do it and the primary reason I traded
my Cubase SX system for PT LE.
Two things strike me about Pro Tools in general.
First, it is incredibly easy to use and flexible. Signal routing is a breeze and you can route just about any signal anywhere without too much trouble. Automation is mature and stable. If you have spent any time with an analog mixer, PT will feel familiar in some respects. After a 12 years on a tascam 4-track, 1 year on n-track, and 2 years on Cubase I was cranking out good PT sessions in less than 6 hours.
Second, it is definately PRO tools- and the price of accessories reflects that. Plugs for PT are ungodly expensive and they don't make lite versions for PT LE home recc'er hobbiests. Make good and sure the PT package you buy comes with a good selection of plugins because you will pay out the wazoo to purchase them later.
(Copy protection is also excellent. If you are the kind who enjoys cracked software you will find VERY little availible for PT.)
I don't know much about PT hardware, but you can't talk about PT LE without mentioning the hardware- LE won't work without it. I only know about the Digi002 since that's what I have.
The Digi002 is a dream come true for me since I work on a PC laptop, but need to transfer sessions to a Mac g4 at times. Its only 8 analog inputs, but can be extended to 18 total via Lightpipe and S/PDIF. It has 4 mic pres with phantom power for purely mobile projects, and I can use outboard pres for more in I need to. For my purposes, which are mostly home-level use with frequent forays into simple pro-level projects, the Digi002 fits the bill perfectly. It ain't pro, for sure, but it just about defines high quality "Pro-sumer."
Take care,
Chris