I see this as another tactic.
What this is enticing is that both sides will view that any further incursions or actions will be deemed unacceptable, and NATO/US/EU cannot support Kiev without making it look like to the international community and Geneva that they are posturing. If at any time shit hits the fan, EU and US can say whatever they like, but the rest of the world will actually see what they are, and Russia would face no further issues internationally supporting anyone whom is against Kiev. They got what they wanted, Crimea, and is walking away with that. Crimea will end up being a massive tourist destination, energy extraction, and shopping market/housing market and thus will churn in massive profits (as long as Russian gov actually spends their money) and it will jump the GDP growth high.
Russia's biggest issue is not lack of money, but too much money sitting aside doing nothing, hence high interest rates. If they use that money in infrastructure and energy development, and having some control in terms of costs of goods in the area, people will flock to purchase properties (beachfront homes, yum!), the area will end up being Russia's biggest in the future. Already the area is booked for the upcoming vacations, so it will obviously end up as a hotspot for travel. If they can deal with the visa system, I bet many more people will go (especially with rouble value dropped, it will be cheaper to vacation in Crimea.
It is no secret that US/EU will place bases in Ukraine and will decide to push free trade. All Russia has to do is drop the WTO, Tarrif Ukraine up the wazoo, and they will be fine. Now they will have a strategic location too, so they do not have to fear losing the whole area.
All the while, Kiev gov will be under spotlight, so any move they make, could spark a conflict and Russia could get away with anything at this point. If EU and US do not oblige and do what they will, then Russia has full rights to whatever.
If EU still decides to push more sanctions, this whole deal will end up going out the window, as Russia would have nothing else to lose. Sanctions will hurt Russia, but it will hurt EU, if not more. EU relies on selling products to Russia, and Russia relies a large portion of the sale of oil/gas to EU. If they embargo, then EU will be scrambling to find an alternative to the loss energy, costing billions if not more, and many banks in EU will end up losing out on billions that Russia invests in. Not to mention majority of the luxury manufacturers sells big in Russia. They will end up losing out. While Russia has options to import from other countries (even custom union countries whom are not embargoes but share free trade with Russia), and switch to whom they sell and invest to/from. As well, like in Iran, it creates new opportunities for domestic companies to fill the gap from loss of trade outside, making more money internally.
This is all pure speculation on my end, but I think Russia did this purposefully in order to see what the EU/US will do next, and it will give Russia the international upper hand (well, to countries who are not sucking on US/EU teets), to do as they deemed necessary to protect their own country and people.