Well, I'm still planning to get new skates in a year or two, but I got a good deal on Qube Juice bearings, normally $32, so I thought I'd try them. I've had them on for about a month now.
They made a HUGE difference! I didn't have the proverbial "skates flying out from under me" experience; they needed about an hour of riding to "break in". I can't say that I'm going faster, since I really can't go any faster at the indoor rink, but I'm noticeably less tired. The rolls are much smoother and more even than the ABEC 5 sealed bearings that came with the skates, and I have a lot less of the "catching" feeling. Freespinning of the wheels last about double the original (8 sec vs. 4 sec), and every wheel freespins the same. More confidence, more control, more maneuverability, faster foot work, all that.
Now, I think a lot of the difference came from the aluminum spacers I got. (Image is from a different vendor; $8 - $16.)
In contrast to the plastic 6-to-8mm spacers, the aluminum spacers allow you to tighten the axles all the way without creating any drag, which means no wobble in the wheels. Much more stable. Much smoother.
Again, I'm not a better skater for having new bearings, but I'm enjoying it more. If you have factory bearings, especially with plastic spacers, I recommend you try new bearings before upgrading the skates.