My issues were not nearly as extreme as yours, but I experienced some occasional app loss, screen freezing briefly on frequent occasions, and random menu pop-ups. The ICS update fixed some, but didn't fix others. My random menu pop-ups were better with the ICS update, then I installed the FH13 update and the random menu pop-ups are back to their odd behavior.
I also never know when GPS is going to work for me. If it decides not to work on whatever occasion I need it, a reboot is usually needed to get it back.
I'm not too impressed with Samsung. My HTC EVO was great the whole time I had it (other than battery life).