I'm a bit uncertain which way to go as far as the software is concerned for a project that we are doing pre-production for.
The style of the project is 2D cartoony (non human), and we absolutely do not want to go the way of toonshaded 3D, as that would involve modeling and rigging a large amount of characters: that is not within our budget (apart from the fact that thus far, I've only animated one short test scene in Maya, and haven't got a clue about texturing, lighting, etc.)

I'm not talking hobby here: we're only a two man production team, but we want to do a professional TV series (short intervals up to 1 minute in length), and both have over twenty years of professional animation experience (I animated on commercials, several European Disney-style animated feature films and directed a children's TV series, my colleage and originator of the project is a key background painter who used to work for Amblimation.) We don't need software with automatic lip syncing or any similar simultated stuff, we do want something with a lot of creative freedom.

There's not going to be the sort of budget that will allow us to hire loads of additional people, or even a Chinese outsource studio, ruling traditional cel animation out.

That is why we chose to go the way of 2D cut out style software.
We're looking for software that is still close to a work style that we're familiar with (x-sheet like tools, hand drawn designs), we'd need controls to fine tune the motion, similar to the graph editor Maya uses, to influence ease in and ease out using bezier curve splines or something similar.
We'd like to use squash, stretch and similar animation techniques, and need to be able to come up with strong poses and goood facial expressions within the limitations of a cut out animation software.

The output of the software needs to be in TV broadcast quality (Probably HDTV)

The things that we're looking for the most is - an intuitive interface.
(The closer working with the software resembles classical cel animation techniques and workflow, the better)
Good, clear workflow.
A good internal structure for file management, scene management
Easy rigging of characters.
Integration of cut out methods with additional hand drawn animation details (Such as headturns, mouthshapes, etc)
An output that still has a traditional feel to it. (I know it's like wishing for the moon, but the closer
we can keep to Disney or classic Tom & Jerry quality the better: we're not talking South Park here, we'd like the actions to be bouncy and cartoony.)
An output of Tiff or Targa files
As the principal animator, I'd need to be able to (singlehandedly) produce about 30 seconds of good, multi-character lipsync character animation with it, including cartoony actions and broad physical humor, that does not immediately look as if cut out software was used for it.

I have played around with a demo version of Toon Boom Solo that has some sophisticated tools,  but tends to get very heavy and sluggish when doing complex characters with highlight layers. The node tree style of rigging may be powerful, but it is quite complex and time-consuming. What I like best about the program is the way in witch you can quickly block your animation and do all fine tuning using the bezier curves there's a lot of control there.
I managed to get close to the quality that we want, but not at the speed we'd hoped for.

Anime Studio Pro uses another type of rigging from what I've seen, more similar to 3D, and seems to be more userfriendly (and defenitely a lot cheaper), and the clips I've seen from Greykid productions were really impressive.) I haven't yet tried it out.
(I know Anime Studio is a bit Poser like in the sense that you can buy ready made characters for it, but that's a way that we absolutely do not wish to go: we' want to use it for our own creations only) 

Does anybody here have any experience with either one of these programs?
Anything to recommend one package above the other, anything that sheds a light about the similarities and differences would be welcome. Or are there even alternatives to these packages?

(We'd rather not use Flash, by the way.)

Thanks in advance for any response.

I have never used Solo, but I have used Anime Studio Pro (I actually wrote a review about it http://www.renderosity.com/news.php?viewStory=13450) and it's very intuitive and user friendly. For cut-out style characters, the rigging system is fast and easy (you just put the bones layer on top of your character layer and you're done).

You should definitely give it a try.

Thanks, Nemirc, I certainly will try it out. Actually, the guy I'm doing this project together with, and who is actually the originator of the project, already bought a single license of the program, just to try it out - for a professional animation package, it is rather inexpensive. (Much more so than Solo at $3000.- per license. I think even Maya Unlimited goes for less these days.)

Even if we would be able to get the sort of results we'd like from Solo, judging from the demo version we played around with, Anime Studio seems to be more intuitive and user friendly, faster, and less taxing on the hardware. I'm certainly going to give it a try.
Rigging in Solo involves wading through ever more complex node trees and gets to be quite daunting for more complex characters, powerful as it may be. I did like the level of control for tweaking and fine tuning the animation, though.
The programs do seem to have quite a different approach to digital cut out style animation. I'm curious to try Anime Studio after finishing my final tryout scene in the Solo-demo. 
Doing 30 seconds of animation per week would be tough using Solo for multi character scenes with layers of body shadows and highlights, making the rigs ridiculously big and sluggish and tedious to wade through in the time line: if Anime Studio has a faster workflow for the same level of quality, and if the software is stable, we'll probably be going for that. I can see possibilities for importing object files as well: as a Poser hobbyist with a 40 Gb runtime I have loads of stock stuff  at hand - even if we would have to limit ourselves to more cartoony objects if we want to avoid a serious style breach.

(Why did they ever name the software Anime Studio? The software is suited for all animation styles, the name actually put me off for a while because I'm really not into Anime style animation, and the name suggested that was all you could create with it.)

Anime Studio used to be Moho from Lost Marble Ltd. Lost Marble had been developing Moho for at least a couple of years before it was sold and renamed. Lost Marble still host the forum

There's a few examples of other professional companies using the software on thr e-frontier site.