I have a 2.2Ghz P4M (the early "M"obile P4 processor) laptop with 1GB of PC266 RAM. Yes, it is slower than an equivalent desktop, with disk access being the most obvious bottle neck, and 32Mb of RAM on the graphics card can be a bit frustrating at times. But, I love being able to work while not sitting at the desktop so much that I probably use the desktop about 5-10% of the time I spend working with 3D (the desktop is a dual processor Athlon MP 2000+ with 2Gb Ram and a Nvidia Quadro 750XGL).

As for heavy use and rendering, I use the laptop all the time for rendering, and have had it running well over 24 hours straight doing renders. I've never had any overheating issues, but I do have a "laptop desk" which is much better than having the laptop sit directly on your lap, or the carpet, or your bed (a real bad idea). My "laptop desk" is simply a portion of the top of a small particle board desk that is cut to fit between the arms of my recliner, with a 1.5 inch lip on one side that helps level the the "desk" surface so the laptop sits at a better angle, and it provides ventilation between the "desk" and my legs to help keep both the laptop, and me cooler. You can find comercially made laptop desks at Best Buy, Comp USA, WalMart, etc. that have built in fans for cooling, and side platforms for a regular mouse (if you get a laptop that uses a desktop processor, one of these would be a good idea).

I would stongly recommend getting a wireless optical USB mouse for your laptop. There are several smaller mice made for use with laptops. They are much better than the built touch pad or joystick for extended/continual use.

If your primary concern is top of the line perfomance, then a laptop may not be what your looking for (although todays laptops can blast the doors off of desktops a couple years old). If convenience and being able to work anywhere is your top priority, then you have to have a laptop.

IMHO, if you use your computer more because it's easier to access, the slight performance boost of a desktop won't even come close to the boost in productivity you'll get from using the laptop more.

__________________________________________________________

My Rendo Gallery ........ My DAZ3D Gallery ........... My DA Gallery ......