Yep, probably the majority use rechargeable batteries.
I don't though.

I prefer the higher voltage from the alkies and such.
I believe the machine operates slightly better and maybe a
tad more stable. But it's not too drastic or anything.
The 250 was designed for 6v, or four standard AA batteries.
If you use rechargeable batteries, you only get 1.2 volts
per cell, vs the 1.5 volts you get from a regular cell.
So if you use the rechargeables you will only get 4.8 volts
for those four cells.
I prefer the slight edge in performance using the full 6 volts.
I get them cheap at a dollar store, so price is not really much
of an issue. Alkies last a long time in the 250. And I change
them at about the 1/2 way mark. Still takes quite a while to
get to that point.
But they seem to do fine on the lower 4.8 volts, so I guess it's
just up to the user. If I had to pay big $$$ for alkies, I might
think different.