Somewhere in Time is my favorite Iron Maiden album. I find it ridiculous that some criticise the album for having too much production magic in it, it's a studio album and artistic product - it shouldn't matter. Maiden made a colossal mistake when they got caught up with this line of thinking themselves and made the weak meat and potatoes record that is No Prayer for the Dying, also alienating Adrian Smith, who had become the second biggest creative force in the band, in the process.
The atmosphere of this album, the explosiveness of the instrumentals put it in a truly special place in the Maiden catalogue. It's Maiden at their melodic best, both in terms of the riffing and harmonies, and in terms of the solos. The dynamic relationship in the rhythm section is spectacular and I think listening to the non-remastered, original 1986 mix of the album really drives that point home - the dynamics of the rhythm section are much more pronounced because they aren't muddled in a louder mix.
As for Bruce, I think the "His heart wasn't in it" angle is overstated. The reason this album feels worse vocally than the other ones during Maiden's 80s run with Bruce is because this is Steve at his worst in terms of writing vocal melodies. It doesn't matter if your heart is in it or not, nobody could've saved the repetitive, unimaginative choruses Steve wrote and the absolutely ridiculous wordiness of Heaven Can Wait and The Loneliness of the Long Distance Runner.