I’ve found Solar Return charts to be very useful for giving a snapshot representation of the energies at play in that year, however I rarely use them alone. I find they very often augment and emphasise the themes that come up in the interpretation of the transits and progressions, which can give you a better idea of where the real action will be.
Personally I don’t understand the Solar Returns – or should I say I don’t know how to interpret them and blend them in with progressions and transits. I believe the natal house that the Solar Return Ascendant falls into could indicate an emphasis on the affairs and concerns of that house for that year, but I can’t say I have seen it working in my life; don’t think there are different themes in my life from year to year – there are only involvements and developments. All affairs are personal (1st house) affairs as far as I am concerned. Then again I do have my Sun sign (Libra) and 7th house (Taurus) ruler Venus in the 1st! And its only aspect is a trine to Mars, my chart ruler (Scorpio Ascendant)!
But think about it: 7th house of relationships of all kinds is very personal, 9th house of foreign travel, beliefs/worldview etc is very personal, 11th house of hopes, aspirations, friendships, the collective etc is very personal. Everything we experience in life is Personal and is there for our Personal growth. We all experience and interpret everything from our own Personal viewpoint.
I find them useful. Sometimess they can offer hints of actual events happening throughout the course of the year in a way that’s uncannily accurate. But as @Liv says, it’s better not to dwell on them too much or else it’s easy to see scary things and turn them into self-fulfilling prophecies.