The base has no use for the Taliban, they filmed walk through the base but that is all. I doubt they stayed the night. This base has no importance to the Taliban, they live among the people so they do NOT need a base. It is NATO forces that need a base, to safeguard them from attacks from the Taliban. Thus the base was left intact, even the troops who abandoned the base saw that it was unimportant to the Taliban, but may be important to them later on so it was left intact FOR OUR TROOPS FUTURE USE not that ob the Taliban.
This is like the situation at the end of Red Cloud's war (1866-1868), the United States agreed to abandon its forts in Powder River valley. As the US Forces left those forts the Dakotas and Cheyenne entered the forts and burned them to the ground. The forts had no importance for the Native Americans, they did NOT need them to hold the area. On the other hand the Forts were needed by US forces to hold the area, thus when abandoned left standing in case US forces would ever need them in the Future. The same with this base, the Taliban has no use for it, thus looked to see what they could pick up and use out of the trash that was left. The US Forces left the base basically intact so it would be easy to rebuild if the US ever wanted to go back.
More on Red Cloud's war:
http://en.wikipedia.org/wiki/Red_Cloud%27s_WarThe above cite mentioned Fetterman's Massacre, one of the last battles in History where one side did NOT use firearms. Chief Red Cloud told his Native Americans NOT to use any firearms in the battle, while the US forces did. The battle was heard from the nearby fort and they knew it was over as the firing of the firearms slowly died out.
As to finding "Ammunition", the main source of supplies for the Viet Cong during the Vietnam War was US trash bins. The US forces would throw away things that the Viet Cong could use. For example the US forces would used batteries in their flash lights and once the batteries would start to deem (This is pre-LED days) would throw out the old batteries and put in new batteries (and when starting patrols would take out old, but still usable batteries for fresh batteries, discarding the old batteries). The Viet Cong would take these old batteries and use them, often as the power source for home made bombs (The batteries still had enough charge to set off the explosive used in the bomb). The Viet Cong would re-use brass cartridges (The Viet Cong AND the Afghans were both know to do this with Russian made Berdan primers, which tend NOT to be re-loadable, given that the US uses Boxer primers in their cartridges it made such reuse easier for Boxer primers are designed for use in re-loadable brass cartridges).
I should note the LAW rocket has made a come back during the recent fighting. The LAW rocket was designed in the 1960s as a replacement for the Korea Era 3.5 inch Bazooka. The LAW was a one time non-re-loadable rocket issued as a Round of Ammunition. IT technically was replaced by a larger more effective anti-tank weapon in the 1990s, but it the recent fighting that larger, more expensive weapon was found to be to large for most soldiers to carry even that the insurgents were NOT using armor. The LAW could do all that the larger rocket could do, but in a more compact size (Yes, the LAW would have trouble with a T-72 Tanks, but no one has been using T-72 against US forces since US forces took Baghdad). Now during Vietnam the Viet Cong would take discarded LAW rocket Tubes and convert them into improvised mortars. Inaccurate but effective in close combat situations. I suspect the Taliban is doing the same (They have access to the same books as the rest of the world does with the internet).
Just a comment on the "Ammunition" found by the Taliban. The US said it left none, and the US forces did NOT leave anything it called Ammunition. On the other hand the US left a lot of trash, trash the Taliban can use either as ammunition or as weapons (or other combat uses, such as tents). The US forces were being drilled in the 1980s on make sure waste was NOT something the other side could use (I was exposed to these ideas in the 1980s when I was in), but I fear that this idea had been forgotten by the troops during the actual fighting AND their officers are NOT make sure waste is waste not only to US forces but also to the Taliban.
My points is the US probably left a lot of what the Troops considered trash.