True, although freezing/unfreezing financial assets is a length of action. The fact that the government was sacked quickly wasn't very surprising, although I wouldn't understand the reasoning behind it.
What comes to it, is that the unification government was actually elected with (I'm not sure how legal, but Fatah is fairly well "known" for being corrupt too) elections, and if it comes down to pointing fingers and figuring out who is a terrorist and whonot, Israel military just shot a Fatah militant a while ago, alledgedly having lead attacks or similar. Why Hamas wouldn't be negotiated with? I have no clue - while the organization's "goal" is to abolish Israel, I'm not sure the political party would share this goal so strongly - after all, they've said that they'd be interesting in negotiating a long-term truce with Israel given that they leave the areas they occupied in 1967. It probably comes down to neither party willing to be the first one not to retaliate, or being the one to back down on demands. Fatah has had it's paramilitary connections too, Black September was linked to it for example - although was denied for obvious reasons. Both factions have their extre sides. It's probably hard to say how the situation in Gaza is at the moment, but I guess Johnston's realease is a positive aspect, especially with him claiming that Hamas is working on things. It's not like negotiating with Yasser Arafat or the rest of the Fatah ever reached any solid results.
The bottom line is, Fatah isn't exactly rose garden, and Hamas isn't any better (both factions are linked to extremeists that will use violence), but if the situation there is improving (given that Johnston got off his 114-day trip with the Jihadists), and Hamas is rooting out some of the extreme groups that evidently are interested in a global war, I'm not sure if an invasion and an interruption of the progress would be a great idea.
edit. In case you're interested, read
Jimmy Carter's views on it - it's a while ago, and by now the situation has already escalated anyways.