"Any personal experiences people have here would be highly appreciated!"
I'm going into my third Sierra season with the original, one entrance model, and can say with confidence that it is a superb 3 season tent for any area that does not get a lot of precipitation. It is easy to pitch, withstands torrential downpours and wind well, and packs down into a very small package. The only real negative that hasn't been addressed with the newer model is condensation. You will get it on the single skin panel that runs down the top of the tent from the cross strut to the foot of the tent. However, that is easily addressed with a bandana or other water absorbent material. I can't speak to how it stands up to snow, but I suspect it would sag, as the panels are very large compared to the number of tie out points. If I were expecting to encounter significant snow, I would add tie out loops to both front and rear panels on both sides at their midpoints to effectively subdivide the panels for loading purposes. Since the newer model has 2 zippered entrances and places the support poles outside the body of the tent, I can see no real areas for improvement if you buy a new one.