Interesting that I see far fewer iPhone folks bashing the s3 here than vice-versa.
I don't know how Samsung is/will be, but HTC doesn't support their phones after launch. I have an HTC Incredible and HTC Thunderbolt. Generally, once most phones are purchased, there's no incentive for the manufacturer to improve it. They already have all the money they can get from you. If something doesn't work today, there's a good chance it wont work later, especially after a newer phone comes out.
The HTC Incredible that I have has 6GB or memory, but it runs out of space to install apps. Turns out there's a 300MB partition that apps can use. Why would someone allow so little space. Makes no sense. Now Pandora won't work on it. Plays a few seconds of a song and skips to the next song. I've tried all sorts of things, scoured the web. Doesn't work.
Thunderbolt, all sorts of software problems with it. After the last update that didn't fix anything noticeable, LTE has been unusable. It constantly connects then disconnects every few seconds if trying to use data. Verizon denies any change to the network. They say the phone is out of warranty, buy a new one. But many people are having the same issue starting at the time of the last update. HTC PROMISED, last year to update to Ice Cream Sandwich. They finally PROMISED to get it done by August 2012. That came and went with no news. The phone spontaneously reboots every couple of days for good measure, usually when I need it. Takes over 5 minutes to reboot.
On the Thunderbolt half the time you try and use voice recognition, it doesn't register your voice at all, as if its not connecting to the mic. Sometimes a second attempt fixes it, but the worst part is it complains at you that you didn't speak loud enough, even if you screamed at it.
Cut and paste is up to each application. HTC copied Apple's approach for their apps, but I use K9 for email and its not very practical in that app.
Thunderbolt and Incredible cameras had good specs, but performance is mediocre at best. Video is choppy, adjusting light levels is jumpy during video making it look really bad. Overall, I certainly can't use it for video, photos in a pinch.
I bought an S3 to give it a good try. Sammy has lots of interesting new ideas. Some are incredibly lame, such as most of the gestures, tilt to zoom? Really? Get serious. Double tap the top of the phone, palm swiping, shaking the phone to refresh, all seem really silly.
But some of the features are interesting. I liked the notepad that you can use with voice recognition. It shows the words as you say them which is really nice, rather than wait until you say you're done.
Nice ideas like picking a word to wake up their Siri imitation. However, I could almost never get that to work.
Reception was much worse than an old Nokia and G1 I have laying around.
After the HTC experiences over the last 3 years, I threw in the towel and have switched to iOS. Apple seems to better support their products over time. They clearly make mistakes, but they generally try to improve over time and support their products.