I lived in 2550 during the first year it was in business.
I waited a while to write a review because I was pretty miffed by the time we moved out on account of all the apartment showings. They sent out renewals about two months after we moved in (like others have mentioned in their reviews) and we decided the price hike wasn't worth it. They ended up showing our apartment about 15 times. It was incredibly frustrating from January to about April, when our unit was finally rented out for the following year.
It wasn't all bad, though. Since moving, I've come to appreciate how soundproofed the apartments are at 2550. I never heard my neighbors - and since our apartment faced Campus Drive - the windows and doors were equipped to block the sound as well.
It's convenient for those who work at UW hospital - and it is right on the bus line. I liked having the outdoor grills, and the mailroom was more secure there than it is in my new building. It's also great that they allow pets.
But like others mentioned, it's pretty expensive considering the location and the fact that half the apartments face one of the busiest roads in Madison - in the end all the policies about trash/bikes/showings just didn't add up to the "luxury" living I felt like I was paying for.
A final note - they told me to get the carpets cleaned upon moving out. The person I had scheduled to come never showed up, so I had to tell the office they would just have to do it and bill me for it. It ended up costing $35 for the office to handle it - whereas the guy I had coming was charging $100, one of the cheaper quotes I found. Leaving the carpets dirty ended up being the cheaper option!