I ended up trying one of these out, it was cheap and we had another small vacuum that took those batteries. IT has worked out VERY well, my only gripe is that it does NOT have an A/C power option just in case, the other HF blue brand does. Other than that it works great even with the smaller batteries and of course even better with the high capacity batts. I have purchased various different attachments for it in and outside of HF and its been an all around good purchase for $70 (minus my add ons).
My biggest issue when vacuuming with shop-vacs is directing the exhaust or using a long enough hose to keep the exhaust out of the vehicle while cleaning it. This has not been an issue with the above machine either. All around I would say its a great addition for ANY garage or shop or even household. Wait for HF sales and you can get it even cheaper making it an even better investment.
I use Milwaukee and still some Portal-cable as far as power tools. The cordless vac that was compatible was great I'm sure, but it simply could not beat the value prop of the HF versions for the application.