Yes - I've been commuting from Brighton to London for work, for about 10-15 years and I have never considered driving into London.
Trains are quite fast and get you directly into the centre if you're lucky - plus you can sit and read a book etc
Downside is cost - so an annual season ticket is the cheapest way, but at over £4,000 a year and rising ...and they are crowded as more and more people commute - sometimes there are no seats and you have to stand!!
Blimey, that's loads...
However, Brighton's well outside of London, and outside the London fare zones - when I lived in Croydon (zone 5), an annual Travelcard (unlimited travel on all trains, buses and tubes in the London area) was about £1700 for the year, although it's probably a little more now.
If you're lucky, a lot of companies based in London are actually now paying for their employees' Travelcards, as they get a tax break for them since they're encouraging use of public transport instead of driving.