George E. Ganss S.J. has produced a nice, modern, readable translation of St. Ignatius Loyola's 'Spiritual Exercises' that the ordinary reader should be comfortable with. In particular, I found the endnotes (Ganss prefers endnotes to footnotes so as not to distract the reader from the flow of the text) most helpful in understanding what St. Ignatius meant in some rather obscure portions of the Exercises. The introductory biography of St. Ignatius also helps place the Exercises in their proper historical and practical context.
The one area where the translation is problematic is in the use of inclusive language. While this works for the large part (e.g. in using gender neutral terms when referring to the reader/retreatant - the original text assumes the person making the Exercises is male), it does become theologically problematic when applied to God (e.g. using 'the Divine Majesty' instead of 'His Divine Majesty'). As long as the reader is mindful of such changes, the translation should not present a problem.
Overall, a worthwhile buy whether you are simply seeking spiritual growth or as a starting point into Ignatian research.