~snip~
If you run it in the background then your PC will slow down and your other work also may slow down. I also don't know how it will affect my PC function in the long run for utilizing CPU power always at higher side. I don't think it is worth at least for myself and don't want to risk my PC to earn these small amounts of bitcoins.
I did quite a bit of testing on this and setting the mining at 20% had no noticeable impact on anything I use on a day to day basis. It really is quite odd that anyone could be worried about the impact of using a processor to do processing. As long as it is properly cooled and the safety cutout systems are all
working to prevent overheating running at 100% is perfectly safe. Running at 20~30% is just normal usage.
I think running at 10% (edit - I meant 100%, not 10%) is not safe for the most of the users who don't have at least air-condition on in their room because your PC/laptop can easily heat up high at normal room temperature and if you run at that high temp then it is not safe for your PC. Again if you reduce to 20 or 30% then your earning will be the very negligible amount.
Edit - typo error.