I've purchased tickets before directly through the
Disneyland website and I actually prefer it over the time-intensive process of using aRes Travel's Disneyland tickets. When you buy your tickets directly from the DL website, if you select the option for electronic tickets, you can print out a piece of paper that has a big bar code on it...1 per person. You take those bar code print outs (those are your tickets) with you to the main gate. The CM scans them and then hands you your regular paper tickets. You do NOT have to stand in line at the ticket booth at all. Just go directly to the main gate.
I've also gone the aRes tickets route and would have to say that for us, personally, it wasn't worth all the hassle. With this option, you have to tell aRes which dates you will be at DL. They will give you a voucher which you then take to the ticket booth (NOT the main gate). If the CM helping you isn't familiar with this type of ticket, then sometimes it takes awhile. In our case, we stood in line for 20 minutes at the ticket booth and then once we got up to a window, it took another 10 minutes to actually get our DL tickets.
Also with aRes tickets, if your travel dates change, then aRes has to issue you new tickets. So let's say that when you bought your aRes DL tickets, there was an awesome deal going on and you got $30 off per ticket (I'm making that # up, BTW). You tell them your travel dates. But then your situation changes and you have to change your travel dates. You have to call aRes Travel to change the dates....they refund you the $$ from the first purchase, then you pay for the new tickets with your new dates. If that smoking $30 off/ticket deal is no longer available at that time, then you have to pay the higher price.
And the tickets are only good for those dates.