I have done it most years but occasionally give it a miss due to pressures elsewhere. I do the BTO version every week uploading the result usually on a Sunday. The main reason for this is that the RSPB one is merely a snapshot which must be of limited value while the BTO one provides a running commentary for the scientists and an ability to spot trends very early. I'm not saying the RSPB one is useless because it clearly isn't or they wouldn't bother and I think it helps draw people into the fold for caring about birds.
PS The BTO one costs me £17 per annum which I think is money well spent.