It's an interesting software package and obviously a bit more complex than Idle Master. They're building a SteamKit instance of Steam rather than relying on the client to determine their "in-game" status. Because of this, it's capable of idling games from multiple accounts at the same time, which is a nice bonus for some people (judging by the number of folks that have emailed me asking if Idle Master can do this). It looks like it also has standard "steam-bot" capabilities where you can easily trade between your alts and easily funnel your cards back to your primary account.
I've not used the software so I can't comment on how well it works. Idle Master has always been a "it's good enough for me, and you might get some use out of it too" kind of software. I do have multiple Steam accounts but I don't redeem my extra games to my alt accounts or anything, I really just use them to test different functionality in Enhanced Steam - for example, "what happens on this page if I own less than 1,000 games?" so that's what I use my alt accounts for.
Obviously, one of the things everyone is worried about with Idle Master is "can Valve detect that I'm doing this?" And while it might be possible for them to determine that you're using Idle Master (based on things like how it switches games, average time per game based on it's card drop rate, etc) it would be significantly easier for Valve to detect something like this other program because from their server-side backend they can literally see you and all of your alt accounts connecting from the same IP, and they can easily track all the trades funneling back to your main account. It seems pretty obvious that they don't care about such things, but it is something to keep in mind when using automation software like this. There were several changes I wanted to make to Idle Master to make it more automated, but ultimately decided against it because I felt it made the system too automated and thus much easier for Valve to detect.
Of course, if you connect to a VAC enabled server while either program is running, Valve can see things like what processes are running in memory and can easily detect if you're running Idle Master or the other program (or any program, really) so that's why I don't recommend doing that. Again, it doesn't seem like Valve cares - so I'd say use the best tool for the job that fits your individual needs the best.