WM5/6 is not XP or vista, its a completly diffrent OS, the most they share in common is like CTRL + C to copy and maybe the registry (has HKLM and HKCU)
my phone does freeze from time to time, but i also have 60x+ 3rd party applications, it takes 400MB on my 2GB microsd card for the applications alone (remember these are mobile applications, supposed to be small but it adds up) however, when i got my phone new it was shipped 2day fedex, i bought my microsd card at the same time as my tytn but it was shipped using EMS (10 days from HK vs 2) i couldnt install anything on my phone other than TCPMP and opera. the phone never froze once, it didnt even go slow. once i installed all those applications (took like 3 hours, thank God for SPB backup so i dont have to do it again) it slowed down a little bit due to the higher usage in ram. when i have like 10 things running at the same time, multitasking it does freeze maybe once a week.
using a MBP and a mac mini at work, i can say those things do not like running more than 10 programs, i always get the pinwheel of death, ive reimage the macmini 2x now becuase when you uninstall and reinstall applications the OS gets totally screwed up.