I commute f/t, it's about 1.15 from door to door. I don't mind it, but it's not brilliant. But then I suspect some of the "it's not brilliant" is because this really isn't my dream job, it's just a job, which in my sector at the moment is better than nothing...
The commute itself isn't too bad most days, if you get a seat then you can learn to use it as "me" time and read, check your emails, MNet etc. And you get used to the length of time quite quickly.
The downsides for me - and maybe most of these won't apply in your situation - are that I'm out the house pretty much all the time my young DC is awake, so at the moment I'm doing that "dad" thing of just coming in and doing bathtime and bedtime. I'm happy working f/t but I'd rather have much less of a commute. Also DP works f/t in London too. We only make childcare work because he does shifts, and we have a VERY supportive CM. if we're both at work then everyone - me, DP, all the grandparents and aunts etc - are over an hour away, which I don't like in emergencies. I've been called back once because DC was very ill and it was horrendous. Oh, and if the train line breaks while we're both at work, we're fucked!
If you have a DH who works nearer, good family support etc then I think it could be a breeze. It's not as easy as driving 20 mins to work, though, which is why I wanted to be honest. But if it is your dream job I'd try it - you can always get another job if you hate the commute.