Well, this is from the Dec. 2000 issue of PC Gamer, and it is about the 4000, the 5000, and the 8000...
Some highlights:
"...all three of the Inspirons we were sent came with 850Mhz Mobile Pentium IIIs, and that speed, combined with the 128MB of PC100 SDRAM and ATI's Rage Mobility chips means that these systems are some of the most powerful mobile computers that money can buy.
That doesn't mean that they have to be fantastic gaming machines, though. ... It means that you shouldn't expect to play many 3D games in true color or at high resolutions. While we were able to play many games acceptably in 16-bit color at resolutions of up to 1024x768 (with some of the graphics effects turned off...) even the 32MB SDRAM I8000 was barely capable of running Quake III in 32-bit color at 800x600. That's certainly better than any other laptop we've ever tested, but it's a far cry from an 850Mhz desktop. What's holding the I8000 back? Mobility, while based on the Rage 128 Pro, is clocked slower than its desktop brethren - it has to be or else it would suck all of the power out of your batteries while on the road. Because of this ... this level of performance isn't terribly surprising. But... truth is, if you need a laptop, all three of these will play your games well - just not as well as a desktop.
In the end, even a fully decked out I8000 isn't going to replace your desktop system. It will come very close when it comes to productivity software, but last time we checked, PC Productivity Magazine wasn't the name of our publication. That said, these are the best laptops available for gaming today and that makes them worth your time, money, and effort if you're in the market for a laptop. Plus, they're from Dell, which means they're very customizable and come with a fantastic three-year warranty.
Highs: Rage Mobility; fastest CPUs on the market today; amazingly good display quality
Lows: Still considerably slower than your average middle to high-end desktop for playing games.
Bottom Line: While not the portable gaming system of our dreams, the Inspiron represents the state of the art as it stands today"
Now, I'm guessing that the new components have made the 8100 better - but generally the same stuff probably applies.
Hope that helps.