Smith would be definitely be a further upgrade in the speed department, but I'd still look to strengthen that position through the draft. Smith is NOT a #1 though. Boldin is the only guy on the roster with that kind of pedigree and thats a concern long term.
With Simpson and Smith getting signed, it looks like Johnson and Crabtree will both be gone. They are practically the same type of receiver (small, not very good speed, but great hands), so it doesn't bother me much. However, I really hope we didn't pay 8 mil for Smith. That's fucking ludicrous if true.