In my first game, small random galaxy, played with normal speed, I spent some 7 hours to research complete tech tree.
For RTS, this is ridiculously slow.
For turn-based 4X Game, this is ridiculously fast. (Or is it? I remember spamming 'end turn' in moo2 and getting large sized games done in 10 hours... guess that's what you get for turtling instead of conquering the galaxy

- then again moo2 is no space empires...)
Right now I'm quite happy with the fleet movement and combat speed on normal speed. Haven't actually even tried fast or slow yet. Also, haven't tried multiplayer, which is obviously where this game should shine.
The major whine in this thread seems to be about the research speed anyway. I see no problem in including 'epic' speed (slower than slow), which would drastically reduce research (and build?) times. I probably wouldn't be playing those myself, though.
The problem is, that for a 'real time' game, you need to keep the game active and up and running. I can understand researchs of 150 turns are easy to manage if you use PBEM or similar turn exchange system once/twice/ten times a day. But it gets quite more annoying if you have to have one computer running SoaSE 24/7 for continuous game -- even more annoying if your playmates won't be wanting that, but instead have to play maybe 2-3 hours a night.
Granted, epic speed would give large games lasting for months, probably years, this way. I, however, would like to play games lasting for 30-50 hours game time (thus, they could be finished over weekend LAN or so) - for me, normal (or slow? Don't know how much slower it is) is quite okay.
But like stated, there's no harm in giving the option for hardcore 4X veterans, is there?