I've been commuting for four years now with my Tern and it's stood up really well to all the abuse with hardly any complaint. However, I only take it on the train, which is one of the double decker ones, with the entire lower deck of one carriage given over to bikes, so the size of the fold is not an issue.
I have on occasion used the trams here and it is fine for that, however, the smaller size of a Brompton would be more suitable.
With regard to the hinge joint, I've had no problems with my hinges in all this time, however, I am quite light even in full winter clothing and work bag. I have a colleague who is really tall and stocky and with a pannier and clothing comes close to the weight limit of these bikes (100kg if memory serves?). He has gone through two hinges on two different Terns, so I would also caution against a Tern or Dahon if your combined weight is getting close to the limit of these frames.
I also use an Ortlieb messenger bag rather than a pannier bag and rack. It will comfortably take a small laptop and all my other work stuff. Not everyone's cup of tea, but I personally prefer it.