I use bank transfers as an option to customers, It is very popular in some areas I work, around 70-80% pay this way in those areas, overall I recon around 40% pay this way, followed by cheque and then cash (If they are in, as I rarely collect)
It cost you nothing so go for it, If you have george for example its easy to keep track of payments.
It varies how quick people pay (as in anything). Some pay the same day, Others can be 1 week, 2 weeks even a month later.
I also offer nochex as a payment option so people can pay by card if they wish, This is stated on my site as being my least preferred option as it charges me to recieve payments and if I withdraw less than £50 it charges me again. Also it takes quite a few days to withdraw into my bank account, But it beats collecting and 4-6 customers a month use it.
With bank transfers the initial payment customers make will take around 3 days to reach your account, But after that it is almost instant, as soon as they make the transfer its in. I have a couple where payment is in before i get home (wish they were all like that!)