And now, some specifics:
For the most part you will be getting the Mikuli edition of Chopin, which is not bad, but it is not Urtext. Once you know the works, you should try to at least borrow an Urtext edition to compare notes.
The etudes and preludes you will get the Paderewski edition, which is good and authoritative, although it can be blamed for being opinionated and a little antiquated in its scholarship.
If your question is more general, I like their Beethoven sonatas (Shenker's Urtex) better than both of the Henle ones, but their volume of Mozart sonatas (Broder, I believe) is much weaker than, say, the Peters urtext.
Their Debussy and Ravel are perfect, and their Bach is pretty good, but not flawless (in Bach the Universal Wiener Urtext is pretty hard to beat, but about twice the price).
Their Scarlatti is ghastly, and their Schubert, Mendelssohn and Schumann wanting. That said, I own these books for a reason.
Once you learn the pieces you owe to yourself to consult all the sources you can, but Dover books are definitely a good place where to start.