What are you going to study?
maedhros5851,
Probably the most important factor in setting your needs is the program you are going to study. For example, liberal arts won't demand the same computer power as engineering. The education discount Apple provides to students is a benefit you need to look into - it might make your decision easier.
If you go the laptop route I would recommend the 12" (iBook or PB), mainly because I carry a 15" PB on business trips around the world. Dragging a 12" around campus would be a lot easier. The question is: will you really need to drag a laptop around campus. If not then I think that the G5 1.6 or 1.8 would be a joy. You can bump the memory up later, if needed, and the risk of theft is dramatically reduced. Just be sure to get AppleCare, regardless of the Mac you choose. If you order a desktop and display at the same time the display will be covered under the desktop order. Also be sure to check out your insurance to ensure your computer is covered while you are incollege.
As far as buying a cheap PC to hold you over, that would be a decision you would you may make based on finances. You would probably get several years out of it, if you get a good brand. I use a Dell in the office and it has done pretty well for me. I did, however, make a support call last week and was transferred to India where the woman was more concerned about getting me to say that the problem (running VERY slow) was fixed than actually fixing it. Now I uderstand why their support has dropped from an "A" rating to a "B". IBM is the only major vendor (besides Apple) with an "A" rating, which would put them at the top of my PC list - I would not go Dell again if I had to buy another PC after that experience.
The other issue you may need to address is a printer. If you don't need color I would recommend finding the least expensive brand name laser printer available. Ink for ink jets cost a fortune!
Have a great time in college! It can be a grand time an experience you will remember for the rest of your life.