I've been having numerous problems with my S3 (display issues), and the two replacements that I've had have been exactly the same.
Now I'm considering a Galaxy Nexus. The £140 saving is appealing, and if I'm only keeping the phone for a couple of years, updates shouldn't be an issue. Question is, is it a good move? To be honest my usage is mainly browsing, calls, texting, no games or even apps of the sort. My main concern is with the new Nexus device(s) coming out, and the price of those. If they're over £400 (ie. they aren't merely spec-bumps of the current devices), then obviously I won't be concerned as the GNex is dirt cheap right now!