I think a lot of people probably struggle with determining if BTL is still worth it.
Probably the biggest gamble is that you don't know what government policy will look like in 1, 2, 5,10+ years from now. My general impression (from reading the news, not as a landlord), is that the government has been slowly turning the screw on BTL investors, and will continue to do so. Although, having said that, they need to be careful not to turn the screw too quickly, as that could cause a mass exodus. And in the area of housing, large step-changes that totally upset the market can be absolutely disastrous. I certainly remember knowing people back around 1990 who were stuck in a negative equity trap. I guess it comes down to working out some margins. For example, if interest rates increase to x.y%, is it still viable? Or if the property is vacant on average for x months per year, is it still viable? The only certainty is that the bigger your deposit is, the greater the margin of safety.
Maybe there is someone on here who has been through the process, and can give a better idea.