So far in the past three weeks my army lists have gone without any time of tank, dreadnought or land speeders in my space marine army.
I have to say the extra bodies are helping greatly. I have been having an easier time holding my own against all races with the exeption of eldar of course. The sad irony is that half my 10k army is put into those things! Having four dreads, a Land Raider, Land Raider Crusader, five pred ani, three pred des, eight rhinos and two Land Speeders.
After playing a good deal of games without them it has come to my opionion that the only good armour so far are venerable dreadnoughts. Any other type gets killed far far too easy with one shot. Smokes are good, but only last once. It comes down to what uses the slots the best and I still find myself shrugging on tanks. Points wise they are sometimes nice and cheap, but I don't feel they have the staying power that eldar has, nor the ability to up their armour stats.
I might just for fun make a tank army again, knowing full well facing those I play who use chaos will die far to fast. Although, I will say that having three preds and then taking the dev trait would be fun. The power you can bear with so much long range attacks would be insane.