Hi
this is exactly why I chose to purchase the iMac G5 17".
I was considering a pc notebook, but wanted to wait for pci-express.
I was also considering 12" PB (too small) or the largest iBook in the same price range, but wanted to wait for G5s.
Then the G5-- pretty portable (about 2.5 times the weight of a big laptop), and better yet, it has no outboard AC/DC brick or wallwart, and I can go bluetooth wireless on the keyboard and mouse.
Think about it, you get:
1) semi-portability
2) a G5 (even the 600Mhz FSB is fast compared to G4s).
3) The price range is basically the same as a top iBook or a bottom powerbook, and you get a full size hard drive.
4) Fullsize hard drive: I knew HD space would be a serious problem with any laptop, but now I ordered the iMac with a 250G drive (or you can plop in your own).
5) 17" monitor (budget wise i'd be limited to the 12" PB but I know I'd be unsatisfied with the 15", and the 17" PB price was way out of my budget)
6) uncramped keyboard
I felt *very* uncomfortable buying a G4-based unit at this late date (wary to be like those folks that bought G3 iBooks just before they were phased out, and are trying OS X on them). The iMac lets me let go this worry, and I get the 17" screen, which was not affordable in the PB line. Obviously if I wanted a tower, I'd easily go for the lower end PM G5s near the same price range, because you'd have expansion potential you would not have in a laptop or iMac (RAM ceiling, HDs, PCI, Graphics), and you forego FW800 & gigabit ethernet.
But for me, semi-portability trumped all of these compromises. To gain portability, I can live with 2G RAM & 250G internal HD, and the currently-passable graphics. The fan noise factor is a minor issue; Other than gaming or long computations, I always run with the CPU on "automatic" mode rather than "highest" because it is unbearably loud when it gets hot.
Note that the 20" version of the iMac G5 is simply too large and too heavy to move around even casually IMHO-- other 20" owners seem to agree in Apple Discussion Forums. Get the 17" if you want portability.
I move it back and forth from my living room to my bedroom several times a week. It's easy: I only unplug the AC, and that's it. I even prop it against the wall on the end of the bed sometimes. If I had a wired keyboard & mouse, this would be incrementally more inconvenient, but probably enough to tip the scale an dmake my iMac moves that much more infrequent. I certainly wouldn't move it from the table to the couch of the same room like I would a laptop.
I'm even considering making a case to take it to the local Starbucks, but I know that's a bit extreme. (But worth it just to blog the photo). However, I wouldn't think twice about bringing it into the car to work for the occasional presentation, although now we're getting more into laptop territory once we get out of the house, largely due to the unprotected monitor (no clamshell) and the fact that the foot & hinge assembly doesn't come off easily, nor does it fold flat. (It requires opening the unit and using a Torx 8). If a 3rd party made a case as well as a custom foot & hinge that comes apart or folds flat, I would buy it in a heartbeat...
Don't worry about the hinge-- it is rock solid, and won't fatigue. The only danger during moving is dropping, or perhaps hitting the monitor on some protruding obstacle, since the unit is more awkward to hold than a laptop.
In a nutshell: it IS a compromise, and almost the perfect one. Much as I like laptops, I have problems with them (monitor, keyboard, drive too small), and I also love desktops and have problems with them too (impossible to casually move). The iMac is in between-- not too small, not too hard to move-- at the same price range. If like me, you have to buy now, there is no question which machine to buy if semi-portability, buying a Mac, and budget are top priorities. If you can wait, then consider the G5 laptops of 2006.