This will be a different fight than we have seen lately. Ukraine is not a failed state, and it's military are not a rabble. They have a sense of righteousness on their side, which is a significant factor. Yet they are up against an enemy which can sweep them aside with a wave of it's hand.
Warriors die for honour. Their worst fear is to leave this world in disgrace. But will anyone come to their assistance?
A few clarifications would be in place:
1) Russia launched an untraditional attack on Ukraine with the aim of annexing as many regions as possible
2) Russia massed on Ukraine's borders about 50,000-60,000 soldiers, brought them up to 95% readiness to launch, BUT with the aim of intimidation. In fact, Russia could not win a shooting war against Ukraine as what we see is almost ALL that Russian Army can deploy now. Yes, it is that WEAK.
3) Russia made a bet on chaos and political disorder in Ukraine. Deployment of SOF to Crimea worked, because nobody dared to resist. Ukrainians had enough forces to squash the Russian SOF (remember Hitler and Rhineland). There were many cases of high treason in Ukrainian top leadership.
4) 2 May 2014 may be the day when tables finally turned on Russia. Russia banked on military threat of invasion to stop Ukrainian government from attacking tefforists-separatists-Russian SOF in Ukraine. Yesterday, Ukrainians realised that they would be royally stuffed anyway if they allowed themselves to be intmidated. Russia would push deeper and deeper in Ukraine anyway. So yesterday Ukrainians started a serious fight-back.
5) Ukrainians need only a limited assistance - intel, secure comms, money. The rest they can do themselves.
6) Now Putin would be damned if he invades, and he would be damned if he didn't. He cannot win. Not invading means he is willing to sacrifice compatriots he promised to protect. Moreover, Putin has unleashed ultra nationalism that is not that different from nazi Germany. That wave might engulf himself. Hence, Ukrainians use the other edge of a double-edged sword against Putin.
So, there.

A few bits of thought I have written in previous weeks:
What I see as a threat emanating from Russia, in light of Ukrainian events, is a type of comprehensive asymmetrical attack. It is not an easy thing to be dealt with in conventional military terms (what good are tanks or artillery in this?), and Ukrainians are clearly struggling to find a workable strategy. Meanwhile, Russians are literally squeezing (and not chopping!) various bits of Ukraine away.
One could call it a “soft power” attack, but that would not be correct either. It is a multidimensional subversion where a military element is employed only when the likelihood of armed resistance is minimised. There are elements of inciting insurgency, economic blockade, military surprise attack, corruption, info ops, political and diplomatic pressure, etc. It is really comprehensive and it hits society across borders with minimum warning time – one could see propaganda, preparations/exercising of a military capability, etc., but not the willingness to launch at any particular moment.
I said yesterday: It is a multidimensional subversion where a military element is employed only when the likelihood of armed resistance is minimised.
My take is that Russians operate primarily SOF in Ukraine and will deploy heavy troops only once the SOF have carried out local coups. If it does not work out, troops assembled on the border could be used for bargaining. The whole thing is set up not like a traditional military op/coercion, but a special op/intel op with multiple paths of development and maximum flexibility. Invasion is a distinct possibility to formalise annexation - once the Ukrainian government has been sufficiently undermined.
If Ukrainian forces do not intervene now – no elections will be held anyway as there will be little left of Ukraine.
If Ukrainian forces do intervene – Russians maintain a threat of a big war and no elections either.
Thinking of having any kind of reasonable elections now may be a major mistake.
It looks like a win-win for Mr Putin. The threat of invasion is, in my mind, an intellectual trap set up for the West who might be pressing Turchinov not to use forces effectively so as to not provoke invasion. The threat of a major conflict is also used to intimidate Kiev itself, and it seems to work quite well.
However, not everyone buys into this logic. The military analysis shows that Putin could not wage a large conflict against Ukraine successfully. He simply is not strong enough to do it. Even limited Ukrainian actions in the east have had visible detrimental effect on so-called people’s uprising and the will of separatists to get on with it. Moreover, people keep pressing Turchinov and Co. to find their stamina and defend the country – and this should not be underestimated.
I have been watching the Western media and news from Ukraine and comparing it to the info from my contacts, and I must say the West seems to underestimate the role of Ukrainian people in this. There is no trust for present rulers in Ukraine and there is an utterly clear sense of growing danger. People of Ukraine will rise and force their rulers to act. They certainly will.
The question is – should one try to play politics in Kiev while losing a massive chunk of the country if not all of it? Perhaps, it would be better to put Kiev on war footing and deal with the “green men” and then have elections.