I was a Flash animator for a decade before switching to Toon Boom. Flash and Adobe were kind to me but there came a time when the things I wanted to do in animation outgrew Flash, which doesn't look like ever improving for animators.
While Flash has its merits, if you're serious about vector illustration and animation I strongly recommend Toon Boom. There are free intro tutorials for Toon Boom on my site: bitey.com. Also check out the work portfolio section for examples, and good luck with whatever you decide!
I have tried TB animate for few weeks and it was a pretty frustrating expirience.The main problem was that the official tutorial on the TB website is just too long and damn too complicated. I came to that conclusion after watching more than 70% of them..They could have explained most of the basics in 15 minutes. As far I can tell, TB is nice software, it has lots of specialised things that are aimed for using in commercial animation where lots of people are involved in production.
The thing is that for doing some simple animation most programs will do just fine. I have come to conclusion that for my occasional amateur animation the best thing I can do is to develop a good Idea that can be animated even with stickmen and still be good. If you dont aim at being animating pro and work in some studio or something similar, i suggest you dont waste too much time with drilling through some complicated programs and tutorials and instead use some simplest tools and have fun in making something.
Toon Boon Studio can be used to replace Illustrator and Flash, Images have mutiple layers, and shapes can be stacked for a number of visual effects, the only thing is that for complex scenes with Animation most of the work has to be done in Toon Boom Studio, cutting shapes to make new shapes and combining is super easy in Toon Boom Studio, just click and drag mostly, one of the coolest features is using gradients with an alpha option to make Glows and Blurs, and if you use a Pen and Tablet you can use the tapering effect of drawing with an Ink Brush like real life, great for character illustration, not to mention the onion skin drawing tools, and if you like import to After Effects for even more options
I'm late to the discussion - but maybe this will be useful to others looking for software to produce animation. I believe any good program which allows you a lot of creative ability is going to have a steep learning curve. The comments below are based on my experience; yours may be different.
I couldn't agree more about Toon Boom. I downloaded the trial, went to the tutorials, and was astonished at the amount of time required by these videos to get any idea how the program worked. Be prepared to invest a couple of days. Also, the tutorials are for the more expensive versions of the program, and so if you're interested in Toon Boom Studio you might might find them somewhat confusing, as not all the options they talk about are available on the cheaper version. Looking at the on-line documentation is MUCH more helpful than the tutorials they offer. It walks you through so you can actually get a taste for the program. Toon Boom will also import Illustrator files which look like the originals (unlike the next program I talk about).
I've used Anime Studio Pro (by Smith Micro) for several months and found the interface unintuitive and, at times, very frustrating. It can produce a great final product, and if you can get past the drawing interface, which, to me, is very quirky (I'm used to Adobe Illustrator), it's a nice program. The manual is helpful, but not great - which means you're stuck with surfing the web for tutorials and the forums (not necessarily a bad thing - just be aware). It's built in physics capability is really nice - clothes, hair, and other things can be made to react to a character's movement automatically, but it takes a lot of experimentation to get it to to work correctly. If you want to import files, it will, but only rasterized and limited vector (You have to save down to Illustrator 8 to import from Illustrator, and the vectors don't look as clean as the original). It's better to build vector art in the program, but, again, this can be frustrating until you learn the oddities of the program. The bone system allows you to connect bones to individual or a group vector points, or can be made to manipulate raster images. Many people produce great stuff with this program and love it, but I found it too frustrating and starting looking for something else.
After seeing some of Daniel Gies's work produced in After Effects I decided to try it out. Right away I was happier because I could import Illustrator and Photoshop files (programs I've used for a long time) directly into AE and they looked exactly like the originals (as well as layers retaining their names and locations). The vector files are rasterized, but if you rescale them the program automatically updates the images to adjust to their new size. There is also a way to paste a vector path directly into the program. Although AE is not a true animation program, it does give you a lot of control. After a month I can see I still have a lot to learn, as the many special effects options in AE can be used to good use in animated projects. I feel as if I have more control over what I am producing, and correcting mistakes seems easier in AE than Anime Studio Pro. I do miss the auto-phyiscs, as well as some of the other features, so in the end it's all about personal taste and what you're comfortable with, and more importantly, your style of animation.
As a final note: I might have been more enthusiastic about Toon Boom if my budget wasn't limited. Toon Boon comes in three flavors ($249, $699, $1,199), where as I already owned AE (CS 5.5) - so your budget, of course, is another factor in choosing. Anime Studio has two flavors; $50 and $300.