Wow! I looked in on this thread quite late, expecting it to be the usual succession of anti-trans rants. But it wasn't!
Shame the only link anyone has provided was to a US-based forum that is primarily for cross-dressers (= cis-men who dress up as women) rather than UK transsexuals. Amongst TS, the overall feeling seems to be that the documentary was better than most, but that it rather sugar-coated the issues: it showed people sailing effortlessly from one high point in their transition process to the next , with plenty of support from loving family and friends. It did not accurately reflect the years spent hanging around on waiting lists or going through the "Real Life Test".
From some of the comments here, there seems to be an assumption that the few seconds that dealt with the science of transsexuality covered all there was to be known, rather than being a tiny snapshot of a growing mass of solid science investigating the structure and functioning of transgendered brains compared with cisgendered brains. If you read the papers (google them -- I've been bitten before for posting links on Mumsnet) you'll see that issues such as plasticity and the effect of cross-sex HRT are discussed.
As for the "does it work" question, the answers are that about 90% are happy with the surgical outcome, with many of the other 10% going back for subsequent surgery to put things right (we're not talking "designer vaginas" here this is things like not being able to pee). A small proportion something like 2% regret having surgery.
Pre-surgery suicide rates vary enormously depending on which part of the population you look at, but the most widely-accepted figures are that about 40% for untreated TS, falling to about 4% post op. Suicide rates amongst post-op TS are certainly higher than in the general population, but this is most likely due to social factors -- difficulty getting a job or housing, alienation from family and former friends, or violence and abuse in general.
In terms of cost-benefit analysis, Gender Realignment Surgery is regarded as one of the most effective treatments available on the NHS. It costs about the same as a hip replacement, but it saves lives and lasts a lifetime.
There is a dispassionate discussion of the clinical and scientific evidence published by the NHS here:
www.engage.england.nhs.uk/consultation/specialised-services-consultation/user_uploads/gendr-ident-policy.pdf