I use storage with my home built boiler. Commissioned in January 2010, I am now on year 8 with the current set up. The boiler capacity is roughly 250 gals, and storage is 300 gals. By OWB standards, my firebox is extremely small at just 8 cu ft, so storage is a must. Also my boiler is not set up with any sort of auto regulating damper, so I batch burn only, usually starting the fire mid afternoon with the water temp between 120 and 130 F, burning "full out" for 6 hours, then shutting it down for the night with water temps at 180 F. Providing it is a "normal" January i.e. average daytime high of -5 C and night time low of -15 C, it seems to work quite well. Last night at - 28 C it was cooler than normal. I shut the fire down at midnight, and it is currently 11 am, outside temp is - 14 C and water temp is 140 F.
My storage is beside the boiler, both in a small separate building (10 ft x 10 ft x 6 ft H), 165 ft from the house. The boiler building is fully insulated, and boiler and storage have 8 inches of insulation. As Willie says, the best place for storage is inside the building you wish to heat, but that is not always possible.
The only pump I have on my system, which does both the house and garage (90 ft away) loops, pumps from the storage tank, through the boiler, to the house and garage and then returns to storage. Advantages are, the pump is handling the "cooler" storage water, and when the boiler is fired, the higher temp heat is pumped directly to the house first.
I burn 6.5 to 7.5 cords per year to heat an older 1500 sq ft farm house and 700 sq ft shop (which is only minimally heated 80% of the time). The wife likes the house T stat > 70 F. I am sure the boiler/storage causes a heat loss, but I am sure I have a higher heat loss with 250 ft of the cheap 3 wrap underground pipe.