Already there have been indepth reviews about the Sheffield Supertram so I'm just going to give you my opinions on it rather than the historical and factual stuff that is already available.

As a student in Sheffield, I have had the pleasure of using the tram to attend exams at Don Valley Stadium and have found the trams cramped, but with so many students attending the exams this is to be expected.

Sheffield City Centre is relatively close to the train station and is a short walk downhill to it, so for people that want to use the tram to visit Meadowhall and are getting on in the city centre, it may be worth walking down to the train station, as there are many regular trains which stop at Meadowhall, in the same place that the tram stops and the ticket on a train is cheaper, and those with a railcard can use this for an even cheaper fare.
The train to Meadowhall is a lot quicker (approx 5mins) as it is one stop away from the city centre, whereas with all the stops for the tram, it can take approx 20 minutes from the city centre to the Meadowhall stop.

Personally I think the trams in France look better and are easier to use as you can buy a ticket before boarding, the last thing you want to do when standing on a cramped tram is to try and find your change for the fare, but the Supertram is a great asset for Sheffield and I should use it more, although it is quite costly in my opinion.

Overall, The trams are useful, but for people just jumping on the tram to go to Meadowhall, I personally would advise taking the train, as it is quicker and cheaper.