I didn't give it much time but I also don't think you could lean against doors and stuff like that either. Was there even a lean button?
I have to wonder how much time you actually spent on the game considering you can't even complete the tutorial without actually leaning, and the tutorial takes up all of 10 minutes.
Guards do have "tap shoes", the sound engine may not be as good as Thief's (but then again, none actually are), but you can easily tell where a guard is by sound alone, how far away they are and what surface they're walking on, even when the sound is muffled by a door.
And yes, the game is not as good as Thief 1 and 2 - the maps lack verticality, there's no mantling, no rope arrow equivalent, no water arrows, no pre-mission purchase screen, no voice acting, the guards are 2D sprites, as are many of the objects, the maps are smaller than the ones in the Thief games (but there is no in-mission saving, so you have to be careful).
Then again, the game was made by one person. One single, passionate developer, and he did a stellar job with the limited resources at hand. The lack of VA didn't bother me because the number of conversations between guards is limited, there's maybe 6 total throughout the campaign.
The author makes up for the lack of voice acting in the cutscenes by turning them into wonderful comic panels:
The art direction was clearly inspired by Bruce Timm's Batman - I heard someone call the art direction of that cartoon Dark Deco, and it's as good a way of describing the artstyle of the game as any.
So, is the game a challenger to the Thief throne? Obviously not. Is it worth the $5 to $8 you are likely to spend on it (or your free time if pirating)? I would say yes. I'm near the end of the game, and having replayed nearly all the missions multiple times (to discover secrets and get the ghost rating) I'm clocking around 14 hours and don't feel like I have wasted my time.