I had the old version up until Mountain Lion broke it and TechSmith demanded more money for an update (more on that in a moment), so I thought I'd see how things had progressed in the time I've been away (basically I skipped the entire v2 of this app).
I do a LOT of screencaptures, and SnagIt is, without a doubt, a very polished application. It's got a lot of new tools and effects since v1, and some (IMO) useless social sharing stuff, but essentially it does what it's always done, and very well indeed: take screen captures and allow you to edit them effortlessly and to a professional standard. The scrolling capture is also an essential tool for me for making records of particular webpages that are not indexed by search engines and which might disappear or change in the future.
That's the good stuff. Now here's the other side. The reason why I stopped using SnagIt back in 2012 was because TechSmith stopped supporting the version I had. As I'd only had it for less than 12 months, I though it was a bit steep. I think it was billed as a $20 upgrade if you had v1, but (as someone from TechSmith says on this page) if you figure they're only going to support the last two OS iterations, and OS X now being on an annual upgrade cycle, you're basically going to be locked into an investment of $20 or so every 2 years.
Moreover, although they throw in a few bits of icing on the cake to justify the demand for more money, what you're really paying for is the right to continue using the app on your machine. If I'm paying $50 for an app, I expect to be able to use it on the same machine for as long as that hardware lasts without having to pay for it again and again. For corporate users and the like the price is chicken feed, but if you're an individual and you get locked into this cycle with ALL your paid-for apps, your expenditure on s/w is going to start to mount.
I'm a part-time developer myself, and I don't necessarily blame TechSmith for this: they've got to spend time and money keeping up with the changes Apple are making, too. But basically, this whole ecosystem is turning into a perpetual money-drain (or money earner depending on which side of the fence you sit) just to keep s/w you've already bought running on the same hardware throughout its lifetime.
Now, in the year and half or more since I gave up using v1 of SnagIt, I've been getting by reasonably well using the built-in screencapture utility (command-shift-4, drag and click) and the free photo editing s/w GIMP. I miss the scrolling screen capture, and it takes me longer to produce edits/annotations that are not quite as cool, but they still do the job. Given the downside of being asked to dig into my pocket every 2-years or so, I thing I'll stick with what I've got.
Summary: yes, this is a polished, professional app that does the job. You won't find anything quite as good on the market. However, be prepared to get locked in to a dependency cycle where you're paying for upgrades on a regular basis. Those upgrades will offer you some new 'features', but essentially you're paying to keep the app working on the same machine.