[HTC Desire S] :
Sorry to hear you are having so many troubles with it. I'm quite enjoying mine (had it two weeks) and I've come from 14 months with the old Desire. I have some theories on your problems. Try these out and see what happens;

1) The 3G aerial is actually built into your battery cover. If this is not fitted properly (as you mention in point 3) perhaps that's why you are getting poor data connection compared to your Wildfire? Check it is seated properly, and check that in putting it on you haven't bent the two small contacts out of place on the underside of the battery lid. I have even better 3G signal with my Desire S than with my Desire, and it suffers no ill effects from any death grip. The wifi issue I can confirm, but from reading other threads it seems that it is more a software problem and a fix is already available for rooted users, and an official one should be on the way. It is to do with the levels that HTC have decided are too weak to use, and they just need tweaking. Apparently the phone will drop a WiFi signal if it drops below something like -88dB which is actually perfectly usable. The people with root can apply a fix which changes it to drop the connection only after -108dB and all the "Death Grip" problems have ceased. It became apparent when an official update for the Desire HD came out recently and THAT phone then started dropping WiFi. It was fine before the update. The devs have dug into the code and found it was this issue. Us non root users can either wait for HTC to patch it, or wait for the unrEVOked team to find a way to get past the signed bootloader.

2) Not had any problems with hitting the volume getting it out of my pocket, but I do keep it in a gel case when out and about which makes them slightly harder to press. Doesn't hitting the rocker just silence the ringtone?

3) See number 1. I agree though it is not the most comfortable thing to remove/attach. I have more trouble getting it off than putting it back on though so I don't think it'll fall off!

4) Battery life. I'm sure you have something seriously wrong here. That sounds like something is really doing something it shouldn't. I'm currently on 11 hours and 27 minutes up time and battery is at 94%! (Wish I could take a screen shot for you!) I'm easily getting 36 hours out of it with heavy use. Like the person who posted just after you, I use Tasker to put the phone into airplane mode between 1am and 7am. Tasker also turns wifi on, turns ringer down and backs off the brightness when I get home. Does the reverse when I leave. It makes a big difference. Also, turn off "Always On Mobile Data", turn off "Pocket Mode" and back off the syncing with HTC Sense if you've signed up to it. I have it set to manual sync. Before I did that it was keeping my phone in partial-wake all the time. It could also possibly be related to your 3G signal battery lid aerial issue. If its struggling to get a strong signal the battery will drain faster.

5) No problems with the camera here. My friend has a Wildfire so I know how it performs. You should be getting much better pics than that. I'm getting better ones than with my old Desire. Camera phones are always poor in low light though. Nothing much can be done about it. Are most of your poor shots indoors? I use PicSay Pro to correct the exposure/brightness/colour levels. Its very good.

If you can't resolve the 3G issues (which I reckon are related to your battery cover not fitting properly) and get the battery drain down, I'd recommend getting it sent back for warranty replacement. You may just have been unlucky.

Hope I've helped some! :)