Hmm timely topic, I just finished brewing my first AG batch after 3 5 gallon batches about 10 minutes ago. I'm going with the small AG batches right now because I don't have a propane burner or a big enough pot yet. I'm working with a 4 gallon pot and a 3 gallon "bubba keg" mash tun. I'd say go for it, what's the worst that could happen? make a mess, learn something, and make some beer?
I was shooting for 2.5 gallons of a Mild Brown, somewhere around 1.038-1.040 OG as a small batch AG test. It worked out well but there were some issues.
Ingredient list:
4 lbs Marris Otter
1 oz Black
1 oz chocolate
0.5oz East Kent for 60 minutes
0.5oz East Kent for 5 minutes
Pitched with White Labs British Ale yeast
My issues I need to work on for next time
1. Boil off rate. I boiled off A LOT more than I expected leaving me with about 1.5gallons of 1.071 wort after a 60 minute boil. This was by far my biggest issue. I had to add 2 quarts of water to bring the OG back down to 1.048.
2. As a result of problem 1 I ended up with 2.25 gallons of wort, not as much as I'd hoped for
3. I was trying to use the hybrid sparging method described above. I don't think I kept enough water on the grains to maximize my efficiency even though it wasn't too bad (68%)
4. I wasn't sure when to stop sparging, so I ran until 1.011 OG. I might have ended up with some tannins, but I'm just going to RDWHAHB.
5. I needed to dough in with another 5 degrees or so and figure out where I'm loosing heat in my cooler. I doughed in with 5.15 quarts of 162 F water and was shooting for 151F but after 5 minutes was down to a 148 F mash, which dropped to 140 after 60 minutes.

I did try and draw some off(the top. Dummy, use the spigot!) to boil and return to the mash, but in hindsight that was a failure