I got my Samsung Focus yesterday and I put a 16GB Kingston Class 4 micro sd card I bought from Amazon and have not noticed any performance issues such as lag, slow loadtimes for apps, or any device re-boots. So far everything seems to be working normal. There is only one annoying issue: I have been navigating the marketplace from the phone and doing a lot downloads, and on two occassions the marketplace froze on me and booted me out to the start screen. I tried getting back into the marketplace but it wouldn't load, the only solution was to restart the phone each time.
*After the Marketplace did this twice and I restarted the phone, I have not had any more issues and have been navigating and downloading apps without any issues. I'm just curious to know if anyone has encountered this?*
Keep in mind the OS is fairly new, I get a small 2 second screen freeze occasionally when I flip from the Zune player to the home tile screen, all the tiles are frozen and in two seconds they all get back to place.
It's happened to me 4 or 5 times today (today beginning at 4AM with heavy marketplace usage throughout the day). After it crashes, I cannot access the Marketplace - when selected, elipses appear to indicate the phone is "working" to launch it but I'm returned to the home screen. I turn the phone off and it temporarily remedies the problem. I've noticed the same bug with Music & Videos on two occasions. I'm using a Samsung Focus with no added memory card.
It happened to me twice yesterday. Each time I was looking at things and then the phone just kind of got stuck and the screen want black. The second time I did a battery pull to get it back from hyperspace.
Today I have not had any problem at all so far so it might have to do with some connectivity issue or some other glitch. Actually yesterday was the first time that it had happened.