Yes, skiing in Deer Valley is lovely. Sundance is a great time to ski

We were also there during the same time as rajuabju and I would echo the sentiments about Jan's on site and the Ski Valet - simply incredible and it made such a difference! We skied in/out straight from the St. Regis (which works for intermediates and above; once the new Burns lift is operational, it should work for beginners too - though not first-timers). The Ski Valet here is how it should be done at other ski in/out lodging. It sounds simple enough but apparently it isn't - yet, St Regis DV has it down! The folks at Jan's got us fitted incredibly quickly and then they took the equipment straight to the ski valet (win!). When we wanted to ski, we gave our name and they brought our boots out and almost every time, offered to help us put them on (win!). They took our shoes away in a tray (win!). They also set up our skis and poles on the snow outside (win!). When we skied back in, someone came out and picked up the skis/poles from us and asked if we were done for the day or going out again (win!). When we came inside, we gave our name and our shoes were brought out in their tray (win!). Almost every time, someone offered to help us get our boots off (win!). And then they took our boots away (win!). I think a key part of this came down to having plenty of staffing in the Ski Valet and Jan's. The equipment was great as well and we reserved the rentals via their website ahead of time and paid when we were fitted. The experience was so great that it carried some drawbacks which I'll get to below...

RIME was incredibly slow at dinner though the food (salmon, halibut) was pretty good. The chocolate cake dessert was fantastic. We did not have any special requests at RIME nor did we have any management meet/greet.
La Stellina (located across from the bottom funicular station) was pretty good as well.
RIME Raw (at the top of the Jordanelle Express and Mountaineer Express) was a great setup but understaffed so the service was slow. The guys were working incredibly hard so I hope management staffs this area better.
St Regis Bar - Their signature Mary was delicious! (The bar is always way too crowded lol)
Concierge - We inquired about some dining but they were not very helpful.
Fitness Center was great and there are complimentary waters here as well as in the Ski Valet

We chose the Plat breakfast amenity yet it was not applied properly and I had to mention it at checkout and then followup with a couple phone calls over the next few days. We did not make good use of the Plat breakfast amenity (it is $40 daily credit - must be used in the morning at the Library or RIME). It can't be used at the Boutique (except for days when the Library is closed).

We did not ask for nor speak to management about a Platinum room upgrade. So it was nice that we were upgraded to a Grand Deluxe room (a little larger at 460sq ft and with slopeside views) after booking the basic room on points. But the check-in experience was not great. We arrived early and had indicated that on the app ahead of time. It was understandable that the room would not be ready but the frustrating part was that the front desk refused to give any ETA on when the room would be ready (other than check in is at 4pm) or offer us a different room (I inquired about an un-upgraded room as we preferred to just be able to settle in). It was the attitude of one of the employees that really soured it for us - she was like a bulldog looking to fight as opposed to trying to help the customer. She said they had no way to know when the room would be ready because it is in a different system. Other properties have had no problem figuring this out. We made the most of the time and skied for a couple hours (we asked for a key to the fitness center to change). BTW, the bell hops were also amazing and they were the ones to suggest using the fitness center to change! We were eventually texted around 4:15pm that our room was ready.

We were celebrating a couple birthdays and mentioned this on the form before our trip. We received some nice treats and cards signed by the staff.

There are timed windows for Tea/Coffee in the Lobby as well as another window for the Hot Cocoa Bar (3pm-5pm). For a luxury property, I would have expected these things to be available all day long. It would have been nice to have some tea while waiting for our room but there was nothing available in the lobby area. We did the smores outside one evening and it was nice. We watched the champagne sabering (5:30pm) once and that was nice as well. I think the $50 daily resort fee is for the Hot Cocoa/Smores/Champagne and the Shuttle service (which we did not utilize - it seemed to be incredibly busy).

I provided much of this same feedback in the survey and received an email full of platitudes.

I mention the negative aspects above so that folks can adjust their expectations accordingly. It is a great hotel and location and it is definitely deserving of it's 4 star rating. After playing this game for while, it is all about managing your expectations. We had an excellent vacation and might return in the future.