FAA has published an update to the AIM, effective 26 May 2016, and it includes a big change if you have an IFR-approved GPS [i.e., a “suitable navigation system” as defined in AC 20-138 and AIM 1-2-3 (b).]
Now, if you fly a conventional approach based on a VOR or NDB (but not a localizer), you can fly the procedure entirely with the GPS, provided you can monitor (using a separate CDI or a bearing pointer) the VOR or NDB facility specified for the approach.
For more information about the use of GPS along the final approach course of a VOR or NDB approach, see Use of GPS on Conventional Approaches (Update)
If you prefer to switch the CDI to “green needles,” see Setting the CDI on a Conventional Approach (The “Kill Switch”) here at BruceAir.
The new language is in section 1−2−3. Use of Suitable Area Navigation (RNAV) Systems on Conventional Procedures and Routes.
The summary of changes to this AIM update notes that:
This change allows for the use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure (IAP) based on a VOR, TACAN, or NDB signal. The underlying NAVAID must be operational and monitored for the final segment course alignment.
The new text in the AIM is in paragraph 5 of AIM 1-2-3:
5. Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.
This change is the result of a discussion at the Aeronautical Charting Forum in 2014.
BruceAir, LLC 
Okay, I’m a little confused. The following Note #4 is still in place, which sounds to me like no procedures have really changed, only the wording to allow the use of a “GPS” needle for final approach segment on a “or GPS” type approach, but the NAVAID must be monitored. See note 4 below and the new note 5 below.
4. Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment. This restriction does not refer to instrument approach procedures with “or GPS” in the title when using GPS or WAAS. These allowances do not apply to procedures that are identified as not authorized (NA) without exception by a NOTAM, as other conditions may still exist and result in a procedure not being available. For example, these allowances do not apply to a procedure associated with an expired or unsatisfactory flight inspection, or is based upon a recently decommissioned NAVAID.
5. Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.
Is this correct? Or am I missing something?
I suspect that note 4 should have been deleted. I have submitted a query to the folks to maintain the AIM asking for clarification. The change described in note 5 is the result of item 14-02-317 in the Instrument Procedures Group of the Aeronautical Charting Forum.
“Substitution” means something special here. See AC 90-108 (https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/946030), 3.g:
Substitute Means of Navigation. The use of information from an RNAV system in lieu
of that from out-of-service conventional NAVAIDs and/or inoperative or not-installed navigation
equipment compatible with conventional NAVAIDs.
Substitution is still prohibited, because the underlying navaid must be operational and monitored.
The history for this change (ACF 14-02-317) is available at https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs400/afs420/acfipg/media/open/Hist_14-02-317.pdf.
Mark makes a good point. I have followed the discussion of this topic at the ACF for a couple of years. I still think that the language in both the AIM and various ACs (especially AC 90-108) should be updated and clarified.