Suite 301 has it's positives and negatives, and is probably only suited to a certain type of visitor or perhaps a certain purpose. I hear a lot of people hating on it, and I don't honestly understand why. The group I was with were not the typical ASU crowd - we had people from Chicago and NY - and we were really impressed with the space visually, and the drinks we had were perfect - no complaints. The Dance floor was slamming, the DJ was great, and the night overall was a tremendous success - and I'm glad we didn't end up hopping to another bar after landing at Sky.
Sky Lounge calls itself "a lounge" - not a "club" nor a "bar." It seems (to me) to be geared toward people who want to socialize, dance, and drink in equal measure (and seems to have plenty of space for a group of any size to do so). I've visited just about every place on Mill, and Sky Lounge takes the cake for cleanliness, wow-factor, and overall enjoyability for someone looking for a chill, more mature atmosphere than you'll find most every other place on Mill.