400 E Randolf is a long established condo building and was once one of the biggest single community buildings in the country. I know that they have changed some board members in the past year and have been renovating some of the common areas, such as the fitness areas.
There is a special assessment at this time in the building for common area improvements. However, most seller's have paid them prior to marketing their home or will pay it at closing. You would have the opportunity to review all financial aspects and the condo association minutes during your attorney review of the building. It was built in 1963, so there is a long track record!
I personally like the building. It is a quiet location right across the street from Millennium Park. It has a great looking lobby and fairly good sized units for the pricing. One of my associates lives there lists many properties... I've even offered on one of his listings in the past.
I think you'll have to decide if this is a good lifestyle for you. The building has many amenities including a rather large pool.