One thing that I've heard that will be included in the next s/w release is the ability to adjust the SD output on the HD DVR. Many have complained that one of the later s/w versions left the SD channels on the 6416 too soft. I did notice a bit of softening. Apparently this was done intentionally. Verizon adjusted some scan settings in that version of the s/w to intentionally soften the SD picture, because their focus groups told them that they preferred that type of picture on their HD TVs when watching an SD channel.
The next s/w upgrade, apparently, will allow you to modify that setting. You'll even be able to shut it off, to go back to what it was BEFORE the last s/w upgrade. Personally, I'm ok with how the box handles SD channels, but I understand what others are saying. Verizon also said that they made major upgrades to the video processing routines in the s/w, to help eliminate artifacts that people were complaining about. Based on my experience - they most certainly did.
Here's the deal. In the past I tried different SD override (4:3 override) settings on my TV, but with some channels both 480p and 'off' resulted in mosquitoing - white dots popping up randomly over my screen. Turning the contrast settings way down on my TV helped, but never got rid of the problem, so I set my 4:3 override to 480i. When Verizon indicated that they upgraded their video processing, I decided to play around with my SD override again. I found out that Verizon was correct - both 480p and 'off' are now artifact-free. As a result, I left my SD override set to 480p. That seems to be the best setting for my TV, and indeed sharpened the SD picture to a decent extent.
BTW, this ONLY seemed to apply to the 6416 HD DVR. My 2500 (SD STB) and DCT700 (digital adapter) are still producing as sharp of SD as ever. In fact, I think it's actually better than it was when I first got FiOS. Hell, that DCT700 even made an ancient TV look good. When they gave those boxes away when they eliminated their analogs, I took one for that TV, which was collecting dust in a spare bedroom. I hooked it up, and was astounded at how good the PQ looked on that ancient 19" (complete with rabbit ears, and an actual dial - 2 of them - one VHF and one UHF).