has anyone got a good tutorial for how to do sprite animations?
There are dozens of very successful 2D-only Unity 3D games. So, no, please don't leave us for Flash. Instead, check out SpriteManager and SpriteManager 2(which costs money). These are all-encompassing sprite solutions that effectively allow you to make a 2D game in a significantly more powerful and versatile engine than Flash.
SpriteManager is here: http://www.unifycommunity.com/wiki/index.php?title=SpriteManager
SM2 can be seen here: http://www.anbsoft.com/middleware/sm2/
What you should not do is use Unity's built-in GUI system to do 2D Games, it's just not designed for it yet.
Their are many ways to do it...
I'd suggest google'ing it.
http://forum.unity3d.com/threads/16763-SpriteManager-draw-lots-of-sprites-in-a-single-draw-call!
That should help...
But just look around, many people have come up with ways to do it.
[http://ezsprite.com/][1]
[1]: http://ezsprite.com/ may have what your looking for