This is asked on MN quite a lot, and people have different thoughts.
To me, one wonderful plus is that I can throw on the oldest, most comfortable PJs clothes and my slippers and a giant hoodie and stay all warm and comfortable whilst getting my work done. I've seen others say it is important to dress as if you are going to the office, as it puts you in the best psychological frame of mind. Of course, it might make a difference if you were expected to do video conferencing or anything 
Another advantage, is that I can stop and take in a parcel, or hang the washing out quite early in the day (so it is dried by the time you would normally get home from a WOTH job). Again, some folk think you must discipline yourself not to do ANYTHING to do with the house or your family or non-work-self during the day.
Because I stop - and have, over the years occasionally gone to fetch one of the dc from school on a rainy day, etc - I am very precise with keeping track of the hours I do, so I have no guilt whatsoever about stopping to prep the dinner and bung it in the slow cooker or whatever, as I know those 15mins just get added back on at the end of the day. I've even been known to have a hair cut if 2pm is the only time my hairdresser can fit me in. But I can evidence where I've put that time back in. I am far more efficient working at home and get really frustrated at all the chatter that goes on in the office nowadays. I 'log off' make a note on my table in my desktop every time I leave my desk when I am at home, whereas, in the office you don't 'log off' every time you go and make a cuppa, or your colleague asks if you saw that programme on the TV last night, so I know I am being incredibly strict on myself, but I like being able to have the autonomy to work the hour I like to, and that "justifies it" to myself.
Other posters on here say they need a break from their desk every hour and work more efficiently for it, and would never not count it as work hours as it is the same as they would do in the office. I guess it deoends on the type of work you are doing and the way you are employed (ie, set hours, or set number of hours, or 'projects completed' type of measures of work).
When you first start working at home, you do need to manage other people's expectations, so you don't get in the habit people saying of "Can you just...... as you are at home"