I actually think the lock/unlock is too loud. Hence while I will mute them in settings. The softer the better, but that is due to personal preference....and I can not stand typing clicks - again, personal preference.
Speaker is much crisper and the audio is louder and less muffled. AmbiSounds (app that plays whitenoise, etc - use it to help sleep at night) sounded clearer than it had on 3G for sure. Pandora sounds MUCH better. iPod/MP3 is not much different to me - but that might have been just been the songs that came on. However, it is still a pinhole speaker. It is great for what you got, but it ain't no boombox.
Connectivity/speed vs 3G is AMAZING! I speculate it is faster than 3GS (wife has - never used much myself). The quick reaction time switching between apps and loading content is blistering fast. One of my most cherished improvements.
No dropped calls - but I've only made a couple, so I am not a reputable source in that manner.