Conservative? Yes. Reformed? Not always.
They are not the top rank of most recent study Bibles in my opinion (cf. ESV Study Bible, Reformation Study Bible). The notes were adapted from the well-regarded, middle of the road, evangelical, NIV Study Bible. As such, they attempt to strike a middle way that neither angers the dispensationalists, Weslyans, or the Reformed. It is "conservative evangelical." Notes are more historical than doctrinal and probably offer more "options" for understanding disputed points. Check out how they deal with the Millennium crux text in Revelation 20:4-5 and the "days of Genesis" in Genesis 1-2.
If you like it, use it. I prefer the massive heft of the ESV Study Bible.
Note that a "study Bible" is usually just a very good reference Bible with historical, archaeological, and interpretational notes layered in at the bottom of the page.
* If you want "textual," translational, grammatical, or interpretative notes, the dirt cheap and MASSIVE 60,000+ notes in the NET Bible (also available online for free) is the best. You will use it for the notes, not for the idiosyncratic translation. I love their NASA satellite maps in the back. Wow!
* If you want an all-in-one study Bible, the ESV Study Bible is the best (and it is Reformed leaning).
* If you want a strictly Reformed Bible, then RC Sproul's Reformation Study Bible is tops.
* Lutherans of a very conservative stripe will find the ESV based and massive Lutheran Study Bible (the CPH conservative one, NOT the Augsburg liberal one) helpful, but they reinforce distinctly Lutheran understandings of the Sacraments on almost every page.
* If what you want is a good concordance and lots of cross-references and don't really care for the notes, get a Thompson system Bible or a R.L. Allan reference Bible. Um-um, they are just like butta.