I came from the Evo 3D, and I'm not a fan of the sound options on this phone either. You have to set in the options whether you want the widget to go to silent or vibrate, it won't cycle through silent/vibrate/ringer. For now, I have downloaded Beautiful Widgets which lets me add a separate widget for silent and one for vibrate.
As for text messages, I use the stock app and find it very annoying that I can only have it vibrate always or never for text messages. In the text message settings, there is a vibrate option. If you check it, the phone always vibrates for text messages regardless of if the volume is set to vibrate or ringer. If you uncheck it, the phone will not vibrate, even if the volume is set to vibrate.
Also, while I'm on the topic of sound, why can't I lower the volume using the rocker on the side of the phone, and have it lower the notification volume too? I turn my volume down to almost silent when I go to sleep, but the notification volume stays turned up loud. The only way to lower it is to go to Settings -> Sound -> Volume. This is ridiculous to have a volume key that will only lower the ringer or the media volume if you are in a game or app.
Hopefully Samsung reads these forums and will fix these issues. This phone has huge potential if Samsung can take care of the small inconveniences.