Puritan Board Sophomore
Aside from accuracy, historical usage, etc., one of the main reasons I prefer the Scottish Psalter is the ease of singing compared with other Psalters. When my wife and I sing in family worship, we never have to pause at a selection, go over the tune, figure out if we know it or could possibly struggle our way through. We just sing.
While not contradicting anything you write here (in fact agreeing with it - the simplicity of the CM tune in SMV is genious), it may be useful for me to say that one of the reasons we went with the psalter we did was because as ex-almost-exclusive-hymn-singers we were able to take up the 2004 RPCI Psalter and use it in the way you desribed because it a) has an excellent tune/psalm index and b) many of the tunes were straightforward hymn tunes that we were well used to - resulting in almost instant usefulness and every psalm having an appropriate tune we knew, without us having to think about an appropriate tune.
Just a point of interest especially useful for family worship application to those 'coming into' psalm singing. To a lessor extent this is a useful feature in The Book of Psalms for Worship as well (see back of psalter) as long as you know the tune names!