Yeah, basically it is like this. DVDs (movies) bought in the store are Dual Layer and have a capacity of ~9 GB (format is known as DVD9), non-Dual Layer DVDs (DVD-R, DVD-RW, DVD+R, DVD+RW) can only write on a single layer and are limited to half the capacity of factory burned DVDs (format is known as DVD5, i.e. ~5GB of storage, although it is more like 4.3GB). The new Dual Layer burners can reach storage capacities of the store bought DVDs. All the Dual Layer burners also burn single layer formats, so by going with a Dual Layer drive you are not necessarily restricted to buying the more expensive blanks. Many of the newer single layer drives can be upgraded to dual layer with a firmwear patch, and may of the Dual Layer drives being marketed today are nothing more than the same old single layer model being sold last month with the firmwear already upgraded.
In anycase a Dual Layer drive can now be had for about the same price as a single layer, so you might as well go with the dual layer even if you will be waiting for the price of the dual layer blanks to drop before making use of that feature. In the mean time just use it as you would the single layer, but know that you are future proofed.
Here is a link to the Dual Layer drive by NEC that I just ordered. It turned out to be the exact same price as their single layer version ~83 US (probably just the single layer hardware with new patch applied).
http://www.newegg.com/app/viewProductDesc.asp?description=27-152-025&depa=0BTW, I order all my stuff from this site as well. Newegg rocks.