I admit bias because my playgroup LOVES removal (and especially wipes), but Creatures without Indestructible and/or "can't be Countered" (and tappers without Haste) are WAY too easy to get rid of without the caster ever getting to use them. For Generator Servant specifically, Hall of the Bandit Lord does the same thing but is far less likely to be worthless (and can also be done more than once), and I wouldn't use that either; enabling mass Haste is not expensive enough more to justify it.
If your playgroup loves removal, then
Sylvan Safekeeper goes
up in usefulness. I'm not convinced by
Generator Servant, myself, but anything that gives haste
can be very potent (I think I, too, would rather use
Hall of the Bandit Lord, but it does enter tapped and take up a land slot). The idea with this guy is that you play him one turn, then next turn you only need 4 mana for Etali who gets to swing right away (or insert big creature/eldrazi/whatever of your choice here). And are people going to use spot removal on that guy? Maybe (if your command is Etali, anyway!), but even if your playgroup use a lot of removal, do they want to use spot removal on every two-drop they see?
So you'd only use it if you were going to win anyway? My point stands; it's not that good.
I don't quite understand... I'd use it to
make sure I win. That seems pretty good to me. It also counters most removal and wipes, making it excellent protection (a smidge less than
Fierce Guardianship for commander specifically, but still pretty excellent), wincons like
Torment of Hailfire, and also
Mystic Remora turn 1,
Smothering Tithe, etc. There's a reason that people run it in cEDH decks.
Being only 1 mana is
huge. There are some zero-mana counterspells, which obviously top that, but holing up 1 blue is not usually too hard, whereas trying to do your thing and also keep 2 open is a lot tougher (and even your 2-mana choices are limited). Maybe in some situations you would rather run
Abjure? I can't really think of anything that does what
Swan Song does as well as
Swan Song does it, though, except
Fierce Guardianship if you're a commander-focused deck.