I'm about week 6 or 7 using the grocery game. Since I'm only a few weeks in I'm definately not an expert, but let me see if I can answer a few questions/clear a few things up.
Doubling coupons - I believe the lists are based on store in your area's specific 'official' policy. If your store only doubles up to .99 then the list will reflect that. For instance, the Albertson's by use just had their big triple couplon weekend. The official policy is to triple up to .75. However, my store 'unofficially' turns $1 off coupons to $2.25 off (very nice by the way, got a 12 pack of soda for .25 due to that

). Any $1 off coupons the list showed this week, were only $1 off when calculating the final price since that was official policy - not the $2.25 I actually got.
Limited space & small families - My house is 2 adults and 1 kid (every other week due to custody agreement). So our grocery shopping is pretty small. I usually by store brands. Also, I have a budgeted amount that I aim for every week when I grocery shop. I say aim for because if I needed laundry soap, dish detergent, tp, paper towels - non food stuff, I always went over. When we first started using the list, I'd go a bit over my budgeted amount. The last few weeks though its been at or below my budgeted amount. As a matter of fact, if I wasn't stocking up on tp and snacks for school this week I wouldn't have had to go grocery shopping and the amount I spent was a lot less than my normal budget. Right now I'd guess that we could go 2 weeks without grocery shopping except for milk & other perishables. Also, I don't have to worry about running out of shampoo, toothpaste, laundry detergent etc and spending too much because its not on sale then. So, for our small family its working. However, when we get back from Disney I do need to reorganize and find more space to stockpile
Overall, I think I could do this on my own if I went to the differnt sites and spent time going over everything. But for me, what I've been saving has been worth paying someone else to spend that time doing it for me.