Yes. I agree about Mendeley.
I have been using it on a daily basis, to organize my references and to read articles and books (using the in-built highlight and annotation function). But there is something a little annoying: for two reasons (to quick add a citation and to read the PDF of an article/book), I used to import PDFs into Mendeley. But this ended up creating duplicates on my hard drive (1 copy of the PDF that one imports, and 1 copy of it that is first uploaded to my Mendely account and then downloaded into a "downloaded" folder which sits inside the program's directory).
Other than that, everything fine.