On the upside, it did introduce us to the canon Eleventh Doctor.
At the time there was a lot of speculation on who the next Doctor would be (get it, that's why its called The Next Doctor, Bravo Davies). Russell T. Davies thought it would be a good idea to try and capitalize on that by making an episode about a guy who believes he's the Doctor and hyping the episode up as if he might be the next Doctor. Well, anyone with a brain knew it was bullshit and a stupid ratings gimmick. It didn't fool me and many other people I saw online at time.
Anyways, once you actually watch the episode you can smell the bullshit coming a mile away. (That is if you didn't smell the bullshit already before) And once it does come its just another extremely retarded cop- out. (Classic RetardTD) The Cybermen also make an appearance in this episode, but in the most retarded way. (Another Classic RetardTD) There's also a lame poorly written female villain controlling the Cybermen or something I haven't seen the episode in years and can barely remember anything.
It's also all steampunk and shit.
Basically, this episode is shit. Avoid.