Some troubles with JavaME:

#1 The biggest: If you want to market the game for JavaME
you have to go get it onto the big portals like Jamba / Jamster,
or Mobile Phone providers.

and this causes #2:

#2 They require the game to be supported for like 80% of the
possible devices, and in different languages.

-> That alone is over your head as an Indy.

#3 Lets say you have 90phones (alls kind of Nokias, Samsungs, SE, Motorolas etc) to test the game on.
-> you will have to make like 4 Category Versions of the game
(very weak, weak, less weak, medium)
Or come to the lowest common denominator engine (leaving you with gametypes like Sudoku or Solitair)

#4Graphics:
there are phones with 128x128 pixel displays,
and phones with 600x400 pixel displays.
->And many many inbetween resolutions

If you dont draw vector graphics, you would have to make different
resolution graphics, and still make some dynamic adaptions
in the rendering.

#5 Memory: some phones have a terribly low Heap-Memory size

#6 Floatingpoint Math:
yes, some phones dont have floating point Math!
You have to do everything using integer calculations.
Maybe simulating floatingpoint Math.

#7quiks:
-> There are many many tiny quiks in the API implementations,
For each you have to make a workaround
Example: Nokia has a big problem using diffent Game Canvases.
While SE does not.

Phones have different Key-Mappings. Some differently than
the API descibes.

Some phones cant use more than a 1-bit alphalayer in pngs...

#8Sound:
You need to support MIDI to get sound on the lowgrade phones.
You cant mix soundFX and MIDI on some devices
Some devices only support SoundFX and not MIDI while running the game.

#9 Some phones can only handle like 10 Classes,
you need to contract a lot of code into a few classes.

#Slow: some phones are just slow, but have (had) a big marketshare.
like the Motorola Razor and many of the Nokias.
(SonyEricsson actually made the way best JavaME phones.)

.....

etc..

You could still sell the game yourself online,
but then: how many people are willing to buy it that way
and are experienced enough to install a jar manually.

Its not going to make much money.

JavaME is somehow "before AppStore tech". Served by only
some remaining big players like Gameloft.

Its still a valid Market though, like in South America.
But whoever want to do gaming is using a smartphone now anyhow.