Question: what is a good download speed kb/s?
Answer: If you mean 150 KB/s (Kilobyte per Second) which equals 1.2 Mb/s, it's not very bad unless you don't want to stream HD videos or download big files. For casual stuff like email, browsing, chatting, music streaming etc, that speed will be more than enough. I would recommend minimum 250 KB/s for better experience.