Designing your product may be a lot of fun. Testing your product with real people offers some stress but generally a lot of positive emotions as you see it being used and hopefully enjoyed. Sometime, though, you have to face the reviewers and bite the pain. Here are my experiences with the different stores.
Google Play: This is my favourite. The process is easy, the website is clear, the review process is straight forward, and the marketing materials required are standard sized. Taking screenshots and answering users questions are the only hard parts -- which devices and sizes are you really targeting? Time: fast.
Apple: There is a lot of red tape involved in beta testing, and it carries over to the store. The website is of high quality, the marketing requirements are more limited (good and bad), the payouts are the highest, but the rejections are more because the reviewers just point you to what rule you broke and not why. For example, "No Apple-specific functionality" or "Don't understand the workflow", when not every app needs sync to iCloud or share on Facebook. Also, when you go to resubmit, it is not often clear what you need to do next because buttons are hidden because Apple wants you to do something (check a box, visit a page on Itunes when you are at developer.apple.com, etc). Time: slow
Kindle: The Amazon app store has recently been improved since it's humble beginnings. Now that they have an SDK to download, a support forum, and other functionality trickling in (in app purchase, some analytics) they are more like a real option for your product. Sometimes the reviewers are erratic or dumb (I've had apps rejected because "tapping the title bar does nothing" [note, the title bar contains the title, and the app functionality is often contained in the bottom 90% of the screen] or "app does not match product image" [using a 320x480 device looks different than a 1280x800 tablet], but generally a good experience. Time: medium
Nook: Barnes and Noble gets high marks for working with developers well. Although they are more picky about what they want in their store (they will review your idea first, then your company's info, then your marketing materials, then your actual app), the support is really quick and they will tell you specifically what to change instead of pointing to a rule book. No real analytics or extras yet, and the site is in Flash (imagine that!), but I think it is a great relationship with above average payouts too. Time: slow
GetJar: Pros: good distribution, especially internationally. Cons: only free apps. I put mine in and took mine out because I don't have the time to support updates on free apps. Time: fast
SlideMe: Pros: easy to use, uses a lot of the same marketing demands as the Google Play store. Cons: no automatic banking and ad options are limited/unclear. You have to submit invoices every time you reach $50 in sales or something like that. If you are an internationally based Android developer, this might be a good option. I don't feel there is enough traffic to justify the work. Time: medium
WebOS: I thought this was a good platform and developer/store experience. Unfortunately, not a good strategy for your business at this time. Time: fast
Samsung: Samsung has an app store that I will target next. Looks pretty good, who knew?
Blackberry: Unknown yet. When I understand what the product is better (Blackberry 10? Playbook? Android, HTML5, J2ME, ?) I will let you know.
Microsoft/Windows8: The Windows Camp events leave me confused, but I have yet to submit to this store. Note: you must use Windows8, new Visual Studio (requires 4gig+ of ram), and the (don't call it Metro) conventions to submit. It has great potential.
Tizen/FireFoxOS -- I plan to and will let you know but this looks promising.
If you have any questions or comments, the floor is yours. I don't know everything, but sharing to help early developers plan their business.
