Yeah the water temp was really the biggest problem I encountered because people kept saying lukewarm. There is a range you want to stay in because if you make it too hot it will fizzle out fast or kill the bacteria (yeast). Also I was impatient with letting the gas build up. Before you see bubbles come through your glass diffusor a foam of yeast/sugar layer will build up on the top of your water. After it gets about 1 inch thick it will start working its way through the airline.
Just to give you an idea my tap water is a steady 7.9-8.0 pH and say I ran the system starting in the morning by night time is can drop ridiculously like 8 to 6.5. That is the downfall with the DIY because there is no regulator normally. What I did to have more control was run my CO2 Air line through a gang valve and adjust the lever to the lowest setting. I turned mine completely off overnight too or you would wake up and you pH would be 6.0. And of course mess with your sugar/yeast mixture to make it work for you. Remember the more yeast the faster it wil eat your sugar and the more often you will have to replace the mixture. I was replacing mine once a week or every week and a half.
You will want to figure out how to run a steady CO2 injection before you add fish. It's really the easiest if you have fish that require soft water.
I say Biorb is a rip off because you can get an air stone for 99cents but since Biorb is the newest trendy thing they can charge you $4 for an air stone. I haven't tried one. I kind of boycott BiOrb and there bubble aquariums because their target market is people who care more about looks than quality of life for fish :)
As far as glass diffusers I get mine from ebay. You can look around for others this is just an example. Here is a link. Live Aquarium Fish Tank Aquatic Plant CO2 Diffuser-AT30 - eBay (item 190453492161 end time Nov-05-10 20:43:06 PDT)
There are many fancy ones to choose from. Some have a bubble cou nter right in them. Also know when you see nano diffusers they are a bit smaller. I have one nano and 2 like the one in this pic. I almost like the nano better just because it is easier to hide. Be gentle with these things they break very very easy..lol.
The benefit of the bubble counter is to get a steady rate of flow. If you didn't have one you wouldn't be able to see if your mixture was making gas unless it was coming from the diffuser. And sometimes your diffusor will get clogged with debris and you would think you needed a new mixture when you really needed to clean your diffuser. Plus it will teach you at what rate you need to keep your CO2. Some say 1 bubble per second is sufficient but I was trying to keep mine as slow as possible to make just enough to push through. It would last long this way and wouldn't give me such a huge pH swing.
Hope I answered everything for you.