There's good and bad here. The bad is that this module provides fewer controls and tweaks than any other midrange model Roland has made. You can't even use an input for any other sound than it's labeled for (using a cymbal input for a tom, for example). You can only control the instrument (within the group type), tuning, muffling and volume.
The good is that the default sounds are by far the best Roland has offered and many don't need tweaking, but dramatic (and very usable) modifications can be made simply with the tuning and muffling controls.
Expensive, but I felt it was worth it. YMMV.

TD-15 was good but TD-25 is a major improvement. It sounds and performs better.

I think TD-25 is pretty cool module. Its 'Super Natural' engine sound got much better and not a joke. If you play snare drum on close to edge side, it sounds like real with overtones, and becomes softer as well. That's amazing in this price range. I love also quick and simple recording function I can use through USB memory. Whenever I need to record some quick reference for other musicians' need, I can go right away. There are no complex buttons and functions to explore for long time, but it's very practical and intuituve to control. I hope Roland updates much more available sounds on it soon.

Do your research! You have to upgrade the firmware on this unit (in most cases) from v1.01 to v1.10 so that you can really unleash the power of this module. It's super easy to do. All you need is a thumbdrive and an internet connection. I downloaded v1.10, extracted it and put the .bin files on my thumb drive as instructed. Pressed F1 with the module off and while holding F1 turned it on... In less than 2 minutes it was done patching. It doubled the number of kits available (from 18 to 36), added additional instruments, added new features (the metronome game that gives you a score based on how well you match it + song to play along with loaded right onto the memory + more stuff I can't remember). On top of all of that, the firmware improved the already incredible performance of this thing in terms of crosstalk (none that I can notice!).

This thing is great. I'm especially geeked about the ability to plug my phone into to play along to my MP3's and even more geeked about being able to plug my PC into it via USB and have it act as a controller for ableton live... I'll have literally an infinite number of sounds, VST's and samples/clips that I can assign to any trigger on the kit. I'm going to have a lot of fun with this thing.

I wouldn't call the price a steal... Seems to be a lot for something like this, but, what do I know... I do think it is a well built, well engineered and full featured product however. So 4 stars, because it could be $750 or less and still give Roland a 500% ROI.

I see no advantages to the TD-25 over the TD-15. In fact it is a step backwards. It has less kits,less fine tuning. I returned the 25 and will keep my 15. The 25 has hardly any documentation with only only s few pages in the manual.