Can't say that I have any experience with the Rossi 851. However there have been several articles in recent years on that very revolver. Wiley Clapp and Gene Gangarossa were the various writers.
Trigger pulls, both DA and SA were measured and were lighter than on S&W model 19s,619s and 620's.Not by much, but they were. Smooth trigger pulls,too.
Fit and finish were considered very good for a revolver that has a budget moniker on it.
The two samples tested had accuracy in the 2.5 in.-3 in. zone at twenty five yards.
Most of the testing mirrors what Native Texan has said.
Nothing wrong with the 82 either except it has the fixed sights. For some that's a negative and others figure most 158gr. loads for the .38 Special will hit at or about to point of aim. There's a lot of truth in that.As always there are exceptions.
For those who shoot a variety of bullet types,weights, and ammo brands, adjustable sights make sense,too.
If this is to be a belt holster gun not used for CCW carry then one does not have to worry about the adjustable sights possibly hanging up on material as it's drawn.
With the Rossi's sights that may not be that much of a problem compared to Taurus revolvers adjustable sights as on the model 66.
Fit and finish were considered adequate to very good.
As far as Rossi revolvers go here's a link with a 'war story' of sorts. If the jeweler couldn't trust Rossi's he'd of never gone out and bought 11 more 351s for his store after the first shooting incident.
http://www.taurusarmed.net/forums/index.php?topic=948.0