Can filtered indexes help improve queries that are based on a time entered or should this be avoided?
BitOff,

It depends on a few factors, there is no one answer for every scenario. For example, you may want to partition and archive some old data onto a dedicated set of disks becvause it is accessed infrequently. I doubt you would consider swapping such a partition for a filtered index. And I doubt you want to create a partition for all the values of NULL in a specific column as opposed to using a filtered index.

You should read the partitioning whitepaper by Kimberley Tripp at http://msdn.microsoft.com/en-us/library/ms345146%28v=sql.90%29.aspx, and the filtered index design guidelines found at http://technet.microsoft.com/en-us/library/cc280372.aspx. 

Those two links should help point you in the right direction as far as all the design considerations you need to take into account.