Solarian has an issue with low Saves, but nothing you can't fix by buying some Feats. And it definitely necessitates Heavy Armor Proficiency if going melee (which you generally should). These combine to make it a tad Feat starved in many cases.
It's also a little MAD, which matters little in the long run, but can hurt somewhat early on.
It does have pretty close to the highest DPR in the game, though, so there's that. And notably better non-combat and utility options than the Soldier by quite a bit (though obviously still not anywhere near as good as something like Envoy or Operative).
Personally, I think it's fine in most cases, though if you have a typical Envoy in the party you're likely better off going with something else, since that tends to eat your non-combat role by being flatly better at it.
Really, any time you're thinking of playing a Full BAB melee character (which is very much its own thing, as choices go), Solarian should be in consideration, with whether you go with that or Soldier coming down to party composition (ie: any other Cha characters around?) and whether you care more about Saves or utility/out of combat options.