Wrong.
http://www.macrumors.com/pages/2003/08/20030809162410.shtml
"The PowerMac G5s were introduced at the World Wide Developer's Conference in June 2003 with shipment dates in August. Some recent rumors have suggested that some PowerMac G5s may have already escaped to some important customers."
Sure, the G4 powerbooks are 'good enough' if you're only using the notebook for 'everyday' tasks, but personally I would expect something better if I'm paying top-dollar for a notebook.
One should also note that Steve Jobs promised (roughly a year and a half ago) that the G5's would be hitting 3GHz by the summer of 2004 (
http://www.themacobserver.com/article/2003/09/17.2.shtml). According to recent rumors, the newly updated powermacs (i.e., ones that *have not yet been released* as of April 2005) will top out at 2.7 GHz. Scaling the speed of the G5 is not Apple's problem, it's IBM's; nevertheless, Apple's hardware is falling further and further behind what is available in the PC world, while they're still charging outrageous prices for it.
The laptop I'm currently using (a 13'' Centrino 1.6GHz) gets warm, but has never once felt 'hot' to me. It spends most of its time plugged into a power outlet, too. I should clarify what I said about the 12'' powerbook: it wasn't the computer (i.e. CPU or GPU, which are all extremely low-voltage components in laptops anyway) that was getting hot, it was the computer's *battery* (which happens to be located right next to the touchpad, at least in the model I was using). Perhaps this explains why Apple needed to recall overheating/exploding batteries in the 15'' model (
https://depot.info.apple.com/batteryexchange/index.html); they apparently have set a very high limit on the amount of heat the battery can put out while charging.
The problem with benchmarks is that programs written for PC's have to be ported to OSX and vice versa; programs will always perform significantly worse when ported to a non-native OS (note that all Adobe programs were originally written for Mac OS; hence why they are always used by Apple in benchmarks). (Another note: for those of you still using Acrobat to read PDF's, look into GhostView... although you only really need it to reas postscript files, GhostView can also read PDF's, and opens in a fraction of a second compared to the ~10 seconds Acrobat 6 takes to open on my laptop). If you want a good example of a Mac's performance on a non-Apple native application that is both CPU- and GPU-hungry, take a look at the Doom 3 benchmarks (yes, it's a game, but it's probably the most floating point-intsneive application out there):
http://www.macworld.com/news/2005/03/02/doom3/index.php
Let's take a number from the dual 2.5GHz powermac with an X800 XT at 1600x1200: 29.5 frames per second. Now let's look for the same number from a PC system with a comparable video card:
http://www.anandtech.com/video/showdoc.aspx?i=2299&p=5
Looking at the top graph (for the X800 XT), the PC is getting 55.4 frames per second... it's 87% faster, and you can probably build a PC of that caliber for <50% the cost of the powermac.
These programs are all involved with media design -- something a med student probably couldn't care less about. Again, these are all mac-native programs and have no point of a comparison on a PC... of course you would expect a proprietary program to run fast if it's designed to be used only on a controlled hardware base.
Most of the computationally-intensive tasks I perform are involved with my research, and it is primarily for this reason that I chose a PC over a mac. My guess would be that well over 99% of (non-commercial, i.e. academic) scientific software was written for Windows and has no cross-platform counterparts. In retrospect, if I'd bought a mac, I would have been screwed, because I wouldn't have been able to use the software I needed.
The mac is a great choice if you only intend to use it as a desktop computer, which is probably the case for most med students. Just keep in mind that you're paying premium prices for technology that would have been relegated to the trash bin a year ago if it was a PC laptop.