First time users
i would suggest that people who get this phone new first do a hard reset. i did that and my phone was much faster.
then i would suggest getting the following programs:
advanced config tool
clear temp (clears temp files)
registry editor (self explanatory)
tman
fp7_ppc_en (flash player)
netcfv35.wm.armv4i (ms .net)
PPCPimbackup
i would say that i only use advanced config tool to do 1 thing, make the GPRS connection auto disconnect. i left everything else as is. open the program, goto menu - more settings - connections. then enable "disconnect after" and select your time.
tman makes sure that when you press the X in the top right hand corner it actually closes said app. normally WM will just minimize. it also has other features as well, but this is the most important 1.
PPCPimbackup is an amazing little utility that will backup all the contents of your phone to a selected folder. its very small and so is the backup. i have 1000+ contacts and 100+ messages and the backup size is 95Kb. it takes less than a minute to backup and the same for restoring. it also goes as far as backing up call record.
if you like the touch diamond type interface, i would suggest trying this
http://www.modaco.com/content/i9x0-omnia-http-omnia-modaco-com/273892/complete-install-guide-for-manila-touchflo-2d-on-i900/. I found it to be quite solid and functional. only problem is that it doesn't have landscape support. but thats ok cause everything else still works.
i really like this device. it really is a powerfull little machine.
i tried the new samsung firmware but it failed

. i am waiting on a response to see if i missed something.
i am also considering loading this custom rom
http://www.modaco.com/content/i9x0-omnia-rom-discussion/274737/update-24-nov-08-custom-rom-manilla2d-with-alternate-landscape-dxhk1-m2d04/ that has M2D preloaded and configured for the omnia.
b.t.w. for those of you worried about the phone getting really hot, i don't think its the battery, but think its actually the CPU.