I have used Photoshop for my custom spriting and animation, but just got this today and found this to be very much helpful in making my animation aligned properly and framed appropriately (I use RPG maker VX ACE, btw). Before, it didn't look bad when I tested my current custom sprites' movements, but this shows me all the directional movements along side each other in the proper frames and it shown me a big difference in the alignments of my previous sprites. Something I would've never noticed, otherwise! And it updates the preview as you work on it.
I highly recommend this as an addition to sprite animation editing, especially if you want to make custom edits, even if they are not the traditional xp/vx size :) It'll let you know if the current grid sizing isn't optimal for what you have (I had imported a custom sheet and though it just barely worked in game, it wasn't the proper size till I fixed it). I may still use my photoshop program for stuff like scenes, very large stuff or minimal to no animated sprites, but this is my new favorite for most character spriting. I also love the ability to layer clothing, hair and items, separating them individually, this is a plus :D And the price is really great, too. Especially compared to another program here on Steam that does something similar. Fortunately it doesn't matter to me if there's limited resources included as I've got tons I've collected and many I plan to make anyways.
Update (and further/clarification tips): Yes, you can adjust the amount of frames to what you need and create a template for more sprites that work in a "similar" manner, if needed. When adding, it'll ask if you want to scale the frames to match, depending on what it is, you would want to select for it to not match so it'll expand properly. Unless it does match, of course (may have to test variations out to be sure). On some clarifications in my post, when I tested my sprites before using this, I was testing animation in photoshop and using the actual rpg maker vx ace engine to test if the sprite would work correctly in it, which was time consuming and ineffecient in itself, since I have to go between programs. Also when I tried to import my "finished" sprite that was made beforehand, it shown me that the framing size wasn't correct (particularly in the middle column, thus cannot be imported properly, if at all), I had to correct it in photoshop by expanding it with the 32px grid sizing requirement to match the outer two columns. This program is best for those that either has a bunch of resources to import/work with or those who are creating their own templates, etc. Even if something isn't aligned right, it's not that hard to go in and make adjustments, just select the layer and make the adjustments. It's a slight learning curve, but not hard to work out. The other program I saw on Steam, cost over/around $100, so this is a great deal once you know how to work it.