I heard that SSD is very bad for p2p apps, such as bit torrent. Is it wise to have a SSD as OS drive on a PC that bit torrent is used a lot on it?
Will I be fine if the target of download is set to the traditional HDD?
I have an SSD and it makes no difference for downloading, as your write speed is still going to be much much faster (even to an older HD) than the download speed going to the disk. The biggest difference (outside of the enormous cost of a sizeable SSD) is that the read speeds are much faster than a typical HDD. Apps on my system nearly all open instantly and load times for games are almost non-existent.