I have a Galaxy S GT-9100 and it works just fine. I can phone with it and send text messages, which is what I use my phone for in 90% of the cases.
The only problem I have for a month or so is that it will not check my POP mail accounts anymore. My Exchange account I use for work still works though, which is more important anyway, so it is only mildly annoying.

As for the robustness I'm not that bothered. I have a plastic cover to protect it when it falls. I suppose it has a real plastic feeling now for some Then again I do not have a phone as a fashion item so I do not care. It is lightweight, which is a pre in my view. Besides that it only has to last for 2 years anyway (of which 1 year has almost past).