I'm no STL homer, but I just picked them up as a second D. For week 1 waivers, there are some specific things I look for by position. For example, I tend to ignore TDs and yards when looking at WRs as these are highly variable and instead look at targets and receptions. I believe those are much more predictive of season-long success. I'd much rather target someone who gets 7/50 than someone who gets 3/50/1.
For D/ST, I look at sacks, who the opponent was, and game flow. Turnovers and TDs are highly variable and can be very misleading. In this case, I'm optimistic about STL and was willing to take a flyer on them because:
1) They totalled 4 sacks (solid)
2) Denver has a decent offense
3) Game flow--Denver was within a TD most of the game and was therefore not forced into excessive predictable passing.
STL' sacks were more impressive given #2 and #3 above. The 5 turnovers they collected are great, but I'm not expecting them to approach that number again this season.
In addition, I like their schedule. They have SF, ARI, DET, and GB the next four weeks, and OAK in the playoffs. Me likey that.