Oh, so not always. I also have problems because the permissive multitasking with N900. I use FM-radio alot, almost daily. I like to surf on the web at the same time while riding a bus. Quite often when using a news portal, I tend to get 2 – 4 windows open and then FM-radio is swapped out. Also if I try to take a photo while listening radio, often FM-radio is swapped out and stops. Sometimes N900 becomes quite unresponsive. I'd rather have web-pages swapped out than FM-radio.
I've tried the same use case with Galaxy Mini quite much during the xmas break. No problem, although I had web pages open, FM-radio listening and camera. Radio did not get swapped out nor failed to play. The device keeps going being responsive. Galaxy Mini does have 128 MB more RAM than N900 though, but that was not the reason it worked because I also opened much more web-windows.
We cannot expect a normal smart phone user to use top or similar programs to monitor what happens in the system to make sure it is fluent to use the device.
N900 was not and is not suitable for a "normal" smart phone user partly because the "real" permissive multitasking. Plain user would not accept the device going unresponsive so often, but would think the device is broken somehow. For us who know what is happening and why, it doesn't matter so much and we can try to avoid the situation by not starting too many processes.