I'm not noticing it on a VERY large project, but my installed RAM is 12GB. The trade-off between RAM and productivity is in the Reshaper's favour IMO.
If its slowing your machine down, there's a few things you can do like turn off code analysis which will help, you can optionally run this later.
As for the additional things it "adds", there's pretty much an option to enable/disable/customise everything.