I was wondering if anyone had an opinion on whether the fit / finish on either a Wilson or Les Baer upper receiver was better than say RRA?  I am planning on purchasing one very soon but don't know whether it is worth the extra $'s.  

Sorry, don't have ant experience with them directly, but everything else they make is first-rate (if pricey). I can vouch for the Olympic Arms parts; they were making receivers for the 2/75 Rangers at Fort Lewis in the 1980's, and I never heard a Ranger complain, and I've used them for years myself with no problems...

I have used most of the major 5 or 6 manufacturers receiver sets, but never Baer or Wilson.  Probably all from the same forge, just different machining techniques.  The RRA's I have used have been excellent, if not too tight.  On two different occaisions I have had to remove .001-.002" on each side of the lug on the upper receiver to get the upper/lower to close properly.  This is not necessarly bad, it made for a perfect, tight fit.  If you have the money and want the name, or for resale value, go for it.  But you won't go wrong with RRA especially for the price.

About a year ago I bought a flattop Les Baer upper without the forward assist for a project gun.  

Finish was black but very flat.  In fact it is the most non-matching of my mis-matched reciever combos due to the ultra-flat black coating.

Fit: I have built more than a few ARs both from kits and as franken-rifles, and this was the first time that I had to really "fit" the upper to a mil-spec lower.  It took some serious work with a mill file to get the lower to mate with the Eagle Arms lower (Or any other of my lowers on hand for that matter -- I checked them all to avoid the filing if at all possible), and we're not talking just the rear lug area either.

In all fairness, after it was done, it is the best fitting upper I have, BUT the anodizing is gone for much of the contact area, and I haven't tried to re-harden or re-color the filed surfaces (they are hidden in the mated area).

I think that Les Baer may form their part with the understanding that they will be custom fitted together for the fit you'd expect from a finished rifle of their price tag, but I was not prepared nor expecting to have to go thru so much effort.

For $108 for a stripped upper without a F/A, next time I'll spend less for a standard one with the F/A and have a drop-in fit and better color match.

Cheers, Otto