Yeah, 3 underrated signings that probably won't make much news.
ESPN had Adams as a top 25 free agent, and he slipped through the initial signings. Bears filled a need there with Tank Johnson likely suspended for the first four games of the season, Tommie Harris coming of the hamstring injury, and the loss of Boone and most likely Ian Scott. Now, the Bears will eventually have Harris, Tank, Adams, and then 3rd rounder Dusty Dvoracek as their top 4 DT's next season - that's solid depth again, and erases what could have been a draft need.
Rueben Brown's signing was expected all along, but he's still playing a Pro Bowl level, and the Bears now return their starting five from last season on the offensive line. I still expect the Bears to use of their top picks, #31 or #37 on another lineman as Brown may have only a season or so left, and Fred Miller is also older now at RT.
Tyrone Carter is a smaller safety, only 5-8, but he provides even more veteran depth with Mike Brown's status up in the air for the start of the season. Daniel Manning could also begin to move to CB although I don't think it will be an immediate move because he'd be buried on the depth chart (as the #4 CB) if he played there full-time next season, but I expect him to get significant time there during training camp.
You have to give credit to Jerry Angelo credit for waiting out the first wave of free agency, and not overpaying like other teams did for average players, and now filling some pressing needs that allow them to now take the best player's in the draft instead of drafting on need.