I haven't heard all of these, but I've heard a pretty fair share. None of them quite stack up to Pet Sounds (few albums do), but there are a bunch of great songs on this weirdly ignored, yet surprisingly prolific, period. Surf's Up and Friends are probably my favorites of the bunch, but I have to admit to owning Carl and the Passions and Holland without having really listened to them more than once or twice each.
Their career arc is pretty fascinating and unique. They're still probably best-known among mainstream listeners for the early, Chuck Berry-aping stuff up through their first big moves toward the experimental with Pet Sounds and "Good Vibrations" and later embarassments like "Kokomo." Somewhat more informed rock listeners will just talk your ear off about Pet Sounds and Smile, as if the stuff before was negligible and the stuff after was nonexistent. Then there's this other audience that's discovered the post-Pet Sounds/Smile 60s and 70s era and (justifiably, I'd argue) approach these recordings almost as if one would approach a forgotten cult artist.
It's like they're three acts in one - the populist surf-rock band that would eventually record "Kokomo" and hit the oldies circuit with Mike Love in charge, the Brian Wilson vehicle that helped him create one masterpiece and one pseudo-masterpiece (I'm not as big on Smile as some are), and a collaborative, forgotten 70s underground pop act (though probably the biggest-selling underground pop act ever due to the fans who stuck with them).
