The G1/HTC Dream like any recent HTC WinMo devices are equipped with more RAM than before. It has 192MB of RAM compared to previous generations which is more like 64/128MB. Of course now we have RAMs up to 288MB but those are ultra high end. On the Android OS (which is what our device runs on and the very reason for all this excitement) uses RAM a little differently from WinMo.
It attempts to populate the RAM as much as it can and dynamically manage the levels of RAM for each program on the fly. This is what I have noticed. Only 96MB of the 192MB of RAM is available to user programs (the remaining 96 I believe is for the OS). On average, it has about 20-30MB of RAM free after a full restart (70% utilization). Each additional program uses a small 10-20kB of RAM. Of course most of the chunks are already loaded in the RAM.
Multi-tasking isn't really a problem because if there's insufficient memory, Android will shut down programs in the background and save its last active state. When the program is recalled, it'll restore its last active state like nothing ever happened. Of course, certain high priority programs will not be shut down. In summary, it is a new way in managing memory.
However, if you plan to use this Android OS for some very serious business maybe that time has not arrive yet. Don't get me wrong, it already has a solid platform and foundation. But its not really as equipped or matured as mainstream mobile OS available now. For example, there's no storage management, no bluetooh data transfer, no video recording, etc. Its solely a good internet centric phone for now and damn good in messaging. If thats all you need, its a no brainer.