Sonic Advance 3 is my least favorite game of the advance series for several reasons.
-I hated the hub world and didn't get the point of them, what was wrong with a level select screen that the first two game had.
-Like what the OP said the game tried to combine both Advance 1 and Advance 2 with the tag team action and as a result the speed element from Advance 2 got lost as there was too many obstacles that would disrupt your speed.
-Using the tag team action was not fun, as it slowed the game down and in cases of bosses left Sonic vulnerable.
-Music isn't as good as the first two Advance game.
-The requirement to get to the special stage was just annoying, people harp on Sonic Advance 2 being bad but Advance 3 is the worse as you need to;
-Find all the chaos in the level and hub world.
-Replay the level to find the key and not die, otherwise the location would reset.
-Find the special stage spring in the hub world.
-Do the special stage, which isn't so bad for the earlier one but the later one, especially special stage 7 can get downright bullshit with its difficulty.
Unlike Sonic Advance 1 and 2 I just don't find the game fun and it's a shame that the Advance series ended on a bum note.
Loved this game, last chaos emerald special stage was BS and getting the key was annoying so I just gave up on it. X_x
Agreed I was once nearly close but I got hit and I was short by 1 ring, I was so pissed off that I just flat out refused to play the game.
It took the effort of my little Brother to get last Chaos Emerald and that was after repeated trial and errors.