The tide has turned rather noticeably, and it now seems almost certain that Ukraine will preserve its independence without experiencing military intervention from Russia.
This article in Russian from a Moscow analyst explains the current situation (English translation).
The analyst confirms much of the geopolitical analysis presented in the previous article I mentioned. In particular, the military, economic, and geostrategic logic of the situation demanded that Russia take over eastern and southern Ukraine and establish a territorial link between Transdnistria and Russia proper. This was the Plan B if Plan A didn't work — returning the entire country of Ukraine to Russia (according to author Dmitriy Oleshnik and other sources).
But neither plan is being undertaken for now, and the Kremlin is left with the symbolic acquisition of Crimea, which affords fairly minimal advantages (a big temporary boost in popularity for Putin) and quite substantial financial and political costs. Even Moscow's insistence on "federalizing" Ukraine — which would allow for the eventual absorption of Russia-leaning territories — is largely being ignored by the West, which is now in a position of greater negotiating power.
Oleshnik states that the Kremlin's strategists miscalculated: 1) the degree of unity the West would reach with regards to Ukraine, and 2) the level of social support for Russian interference (lower than expected).
Now Russia is drawing troops back from Ukraine's borders and signaling that it has no intention to intervene militarily in Ukraine. It may still be involved in attempts to sabotage the upcoming May 25 presidential election, but that is starting to look like a more and more difficult task as the new Ukrainian political environment solidifies and the Ukrainian military machine becomes more effective at countering external attempts to destabilize the situation in Ukraine.
What would it take to keep the election from happening? Officially — war or a state of emergency. A plausible way to get Kiev to announce a state of emergency is to create large disruptions through active separatist groups, violence, etc. around Ukraine. An explanation of how Russia might still attempt to make the most out of the current situation is given here by Illarionov (English translation). For some reason I find this increasingly unlikely, but it must be considered a very real possibility.
Ironically, by drawing Crimea's 1.5 million pro-Russia voters out of electorate, the Kremlin has substantially decreased the likelihood that the next president will come from the eastern industrial regions, where Russia has more leverage.