I am currently a student of Electrical Engineering and I love my macs. Heck many of my classmates who don't have macs want macs and some have already ditched their crappy windows computers. I have a 1st gen macbook, but I also have a 17" MBP i5 which is most excellent. I use Parallels 5 and thus I run Windows XP and Fedora 13 in VMs and they run really well, thus I have no problem running any software and I don't have to worry about windows trashing my machine. For less demanding windows programs I just run them under CrossOver (basically a paid version of wine), programs like MicroCap run great under crossover, thus I don't even have to start my VM. The programs that I use everyday for school run natively under OS X. These programs include, Mathematica, MATLAB, MacTex 2009 + TeXShop, LaTeXiT, Xcircuit, MacSpice, VectorDesigner, Pixelmator, iWorks (pages, keynote and numbers), Adobe illustrator, . . . etc, plus I can run lots of linux tools to with macports. Although I VM into fedora for FEL (Fedora Electronics Lab), and use windows for MPLab (for programming PIC chips) and for some Keithly tools for the SMUs, but most of the SMUs I can just control via a web browser.
Electrical Engineering is hard enough, why have to fight with windows bull crap everyday :) and yeah I am a long time Windows user, so don't think I am some nut who has been on macs my whole life and has never seen the other side. Although sadly I still get conned into fixing windows problems all the time. Oh one other thing writing code on the mac is soo nice, with xcode or just the terminal.
As for which mac to buy, I have managed just fine with my old macbook but if you can afford a 15" MBP with an i5 then do that, as the i5 is one really amazing processor IMO. Also with 4GB of ram in the base model you shouldn't have much trouble with at least 1 VM running, although I can have all 3 OSs running at the same time if I really want to. But 99% of the time I am just using OS X (although it used to be more like 80% as I used to have to use MPLab almost everyday and Altera's Quartis, but I should mention its possible to program PICs from OS X too, but I tend to choose whichever OS has the best tools for any given job, as I want it to work and be easy).