To correct a few things from earlier - No GameCube games (at all) and Excite Truck/Battalion Wars II were never eligible for coins.
Excite Truck was about two years old and Battalion Wars 2 was about a year old when Club Nintendo launched. With very few exceptions, only Wii and DS games that were still "In print" at the time were eligible for coins... for example, all four major versions of Nintendogs got coins, but the "Best Friends" edition did not.
For the concern about 3DS post-play surveys going down by ten coins - a good chunk of 3DS registration surveys are going UP by ten coins as well. Consider this when making the decision to cash in.
As for these new coin values... guh. I had 49 "to dos", 22 games and 570 coins already sitting in my account. I was up until I literally fell asleep sitting up last night doing surveys. I had already created a spreadsheet to help determine what year my various surveys ended, so I had to use that to compare old vs. new coin values to see which games needed to be registered now and which surveys I had to complete now to maximize my return in coin value.
Thankfully, I'll still have more than enough to get my ceremonial Day 1 Platinum just as I have had for four years now.
Sadly, this means that I'm going to have a bunch of coins all expire at once if Nintendo doesn't put some awesome prizes up in the next two years...