When you factor in the management fee, these "cheap to NAV" closed end funds often start looking less interesting. Take, WIW. It's management fee is about 50bps higher than comparable Vanguard. Multiply that by a duration of 10yrs, and all of a sudden it's only 5% cheap to NAV instead of 10%. Now consider that the fund is only 70% TIPs along with 12% cash and other assorted bonds. In times of distress, the discount to NAV is likely to increase, making it a poor hedge (one of the primary purposes of treasuries). It's not to say this fund is awful, but given it's drawbacks, it's probably not too compelling.
It's worth underscoring that TIPs have NEGATIVE REAL YIELDS. You are paying money for the privilege of reproducing inflation (i.e. you will underperformed inflation). If you have a decent horizon, things like stocks and real estate are better assets.