I just finished my first "full" Polaris experience (Polaris Lounge, 77W with new seats). I have to say I am overall very impressed.
The SFO PL was an excellent lounge, and not particularly crowded during my 20 minutes there. The new seat is a very impressive hard product. It has its drawbacks (yes, I hit my knees on the tray table, and it's a little bit cramped in the vein of the new LX J seats), but overall I was extremely impressed with the hard product quality when compared with the seat density. Obviously I would prefer the legacy GF seat for the increased shoulder and knee room, but I think it is to the Polaris seat's credit that I am even comparing it to an F hard product.
The food/wine/service is of course the UA normal.. no amount of rebranding is going to change that. The idea behind Polaris though was supposed to be quality of sleep, and I think they do an excellent job delivering on that. The seats are quite wide across the shoulders, and the bedding is of course top-notch. If it weren't such an awfully timed flight (SFO-FRA), I would expect to sleep almost as well as in a hotel.
All in all, evaluating the "full" product, I am very happy with the execution of the announced concept. UA is never going to match some foreign carriers for soft product, but I think Polaris does well at what it is shooting for, and the high-density, large cabin will mean a continued source of low fares and upgrades.