I have a Daiwa Tierra baitcaster I'm thinking of sending off to have the bearings upgraded (probably to Reelmechanic since he seems to be the most recommended on these forums) but I got to thinking, is it possible to upgrade spinning reel bearings?

I know it's done in baitcasters for primarily casting reasons but I can't help think new bearings in a spinning reel could really make a difference in smoothness.

Anyone ever done this or am I out in right field for thinking about it?

Unless the stock stainless bearings are damaged, there would be no improvement to smoothness going to a ceramic bearing.  It would actually not be as smooth.  Stainless for smoothness, ceramics for speed.

Stainless for smoothness, ceramics for speed.

I agree 100%. Also I haven't seen a bc spool support system in an actual cast yet that needed ceramics (MPO). Maybe an ABEC5 and like you said in stainless

As far as upgrading the spinning reel bearings, usually a good servicing can make a spinning reel smoother.

The main pinion bearings and sometimes 2 crank support bearings, everything else is now oscillation drive support and line roller support. Oh and just remembered the crank paddle.

Clean them all out well, re-assemble with the proper amount of lubrication and see what they feel like then...

Tight Lines All!!!  

Unless the stock stainless bearings are damaged, there would be no improvement to smoothness going to a ceramic bearing. It would actually not be as smooth. Stainless for smoothness, ceramics for speed.

as in high spool speed when casting?

You got it.