I like Sims-Walker and Boldin a lot as sleeper guys to perform better than expected this season. I also do not like Austin Collie at all. That being said, I think Foster, injured hamstring or not, is much better than Hillis and makes the deal worth it.
I'll be trading Deion Branch in Sims-Walker's place, per the others request, which I agree, makes this a better trade on my end. See OPs date.