Now, his W is great for farming, and also for pushing, but I find it mediocre for lane control/bullying, and too little damage to be a real impact on fights.
The ion shell at lvl4 does more damage than the radiance, in fact almost twice the damage, 50 vs 90 dmg/sec. Now this dmg is unreliable since it depends on the ion shell carrier to be near the enemy but imagine an axe blinking in and calling with an ion shell, thats 450 dmg/sec done to the enemy team plus axe's spins.
As for lane control it allows for excellent lane control. If the enemy team is pushing hard put the shell on an enemy melee creep with full health, thus they can't deny it. It also hurts melee heroes who try to last hit. If they have ranged heroes put the shell on the enemy ranged creep. Now they cant stand behind their creep wave and the ion shell is just out of range from the melee creeps so it wont push the lane. They have to move to the side of the creep wave which means they are in a better position for you to harrass or for someone else to gank.
What to do if they use the pull camp alot?
Put an ion shell in their stacked pull camp, ka-ching! They might pull every other wave, well you should help them out. Pull every wave for them if possible. Put an ion shell on it. Now they have to tank your creeps under the tower or pull them back behind the tower where you have put an ion shell on their incoming creeps, either way they take alot of damage. You should be able to stay in XP range during this whole time and dart in and out with surge.
If you feel like pushing you put the ion shell on your self or on one of your full health melee creeps. Also get in behind the enemy tower and pull the creep wave into the pull camp and ion shell them. Kaaa-ching!
If you somehow are completely bullied out of lane, the only time this will happen is if they have 2-3 stuns in lane. You can always jungle easily with the ion shell.
If you want to bully someone in lane ion shell and surge yourself, run circles around them while the ion shell does it's thing.
Even better lane with an invis hero and put the shell on him. If the opposition has not been subjected to this trick before they will give you 1-2 easy kills before they get the hang of it. I think the most kills i've gotten in a game in the early lane stage with the invis hero ion shell trick is 5. He just ran in circles and couldn't understand why his health kept going down. If you find an invis rune you can do it yourself, just ion shell and surge yourself before picking it up, if you don't have a bottle.
Ion shell is never not useful.