Let me try and clear up a few things here.
First, Robinsons health. In 2000 he hurt his back and had surgery but came back from that. In 2001, he was rounding back into shape and then in week 5 he tore knee ligaments. Now we all acknowledge that it takes approx. 18 months to return fully from a knee injury. That 18 month window ended in the past month since sometime in Feb or Mar would have been 18 months since the injury. As a result, he should be 100% again.
Second, the depth chart issue. Week 5 in 2001 he hurts the knee and when camp started in 2002, he was only about 9 months from the injury date. As a result his preseason was pretty uneventful as they were trying to go easy on him due to the knee. Marty Booker and Dez White opened the season as the Bears starting WRs with bonus baby David Terrell as the #3. Robinson was #4, not because he has no talent but because he wasn't even a year off knee surgery. When Terrell went down with a foot injury, Robinson was bumped up to #3.
Third, his production last year. Robinson restructed his contract last year and a clause said if he got 35 catches, he would be a UFA. There was some speculation going around that the Bears were intentionally not throwing him the ball in order to not trigger the clause. Also, take a long look at the Bears offense as a whole. Last year, the Bears QBs were Jim Miller (noodle arm), Chris Chandelier and Henry Burris (yeah THAT Henry Burris). Not exactly a who's who of the NFL QB family. Miller and Chandelier are fragile guys playing behind an Oline who at one point had lost 4 starters and most of the season played with only 2 starters from the season's beginning. Not to mention the idiotic Bears offensive scheme which doesn't play into Robinson's strengths...or even Terrell's.
Here is why I think he will be a very good pickup. He will be back 100% healthy from the knee so that isn't an issue. In 99, he had 84 catches for 1400 yards and I think 9 TDs in his second year in the league (and IMO he wasn't even hitting his peak yet and was on a pace in 2000 to do the same statistically). Does that sound a little bit like a certain WR that was wearing Cardinal red recently? He is a good person off the field as witnessed by his receiving the Brian Piccolo Award for Excellent Play and Exemplary Leadership and Character (not an award just given out with no basis). He will have a chip on his shoulder to prove he is a top line #1 WR.