No problem. I’ve use it to clean customer systems and It will find things that Spybot, Super Anti-Spyware, and MalwareBytes will miss.
About speed when it was new, Ever since the recently discovered Meltdown/Specter fiasco, New patches have been released that, depending on the system, can reduce performance drastically if the processor is old. From what I understand, this performance loss is mostly found in Intel based systems. If the system is 5 years or newer, most likely, depending on the vendor, there will be a bios update that updates the CPU microcode to coincide with the Specter/Meltdown Windows patch.
Systems that experience the least amount of performance impact begin with Intel systems based on Haswell architecture, 4th generation i3/i5/i7 on up. The absolute least performance degradation is seen on the 8th generation or newer processors. (Less than 10% performance loss) Skylake 6th generation processors can experience up to a 10% hit in performance. This is only noticeable if you are already taxing your processor with maximum thread counts.
Using Windows 10 can reduce this performance loss a little bit verses Windows 7.
AMD appears to be effected by the Meltdown/Specter flaw, however AMD processors do not experience a performance hit like the Intel based CPUs. Specter exploit does not effect AMD systems remotely.