Well what a great thread you have all started here for my 2 pence;
All the good musicians I know have one thing in common -none of them sit down and think 'right I'm going to practice' most of us (and I'm sure this goes for all of you) want to pick up their bass as soon as they see it. I'm sure you all have got in from work and picked up your axe started playing with the intention of doing something else only to 'come round' 4 hours later standing in the dark, desperate for the lav and starving hungry with sore fingers!
For me the greatest aids to developing technique are;
A single minded determination to get it perfect (you've all practiced the same thing over and over again for hours until it's right and until everyone else within 60ft is sick of hearing the same 20 notes again and again)
Joining a band (playing with a drummer whose understanding of your technique becomes almost telepathic over time is an awesome feeling)
Learning that timing is the holy grail, not fancy technique or speed(many still ignore this and are worse for it)
Improvising Live (learn your scales or just what sounds right and get up at the local club and jam, any bass player worth his salt should be able to jam 12 bar as a minimum, oh and it's super cool)
If you do these things your ability will develop almost without you noticing and all of a sudden after 13 years of playing you will think 'blimey I'm actually pretty good!'
All these fancy chops are great they are like a little sideline for bass players to wow each other with; but to use and analogy the World Footballer of the year is Fabio Cannavaro (a quietly effective central defender) not Ronaldinho or Cristiano Ronaldo despite their flicks and tricks. Cannavaro won this cos' he got the job done and his team and won the World Cup. As a bass player you are the central defence, you'll never get that much praise but when you and the drummer do your job right you will sound awesome. Let the lead guitarist and the singer do the musical equivalent of stepovers and Cruyff turns whilst you do the real work. If your not satisfied with doing that role exceptionally well then my son, you ain't no bass player, go and learn the guitar.
Finally, despite having learned every style I have been able to; fingers, slaping popping, tapping etc etc, when I come back to playing with the guys I have played with since I was 17 out comes my plectrum because that's the sound and style I want, and no amount of mocking about playing with a plectrum not being proper will stop me.
For me what makes a bass player good is when he understands the right part is the appropriate part to the music as a whole, played in time,in tune and tight, nothing more; get this right and everything else is just a bonus.