Feature:
The most useful feature is the groove control. Here, you are given a bunch of standard midi files that correspond to the loops. This means you can drop the SMF into your MIDI sequencer and change the grooves to your liking, even add fills, etc. The disadvantage, as was pointed out in another review, is that you can't change the drum kit that corresponds with the particular SMF. So if you want to add new drum sounds, you must use a separate sequencer track with a second instance of Stylus set to a different kit. And if all of the drums you want aren't in that kit, then you might need a third or fourth track, etc.

Quality:
Stylus does not use up a lot of memory or CPU, so it works pretty well on slower machines. I used it on a 1 GHz PIII with 512 MB and it ran fairly reliably.

Value:
Now that the price of Stylus has fallen (it used to sell for $299) it's more appealing than it used to be. And if you are primarily doing hiphop, it's probably great.

Desirability:
It's undoubtedly merely practical. There are many other ways to get good drums into your sequences. It's a great "extra thing" to have in your arsenal if you can get it at a really low cost (but not used!!!!), but unless you're doing exclusively hiphop it's probably not going to be the only thing you'll ever need.

Sound:
The sound quality is excellent, however it ONLY contains hiphop beats, NO rock or alternative beats at all. It's great if you're doing rap, dance, etc., but completely useless if you're doing rock, alternative, metal, jazz, blues, folk, songwriting, or arguably even techno styles.

Support:
BE FOREWARNED - Unlike most other software companies, Spectrasonics licensing agreement does NOT allow you to sell your software to someone else once you've gotten tired of it. And yet, there are often second hand copies available via the usual used channels. This is particularly a problem for the buyers of second hand Spectrasonics products, since they often unwittingly purchase the discs used without even knowing they aren't technically allowed to buy them. When you buy any used Spectrasonics product, the buyer must pay an additional $50 fee to register the product or it won't work. And not only that, once you've paid the fee you are still NOT ALLOWED TO PURCHASE UPGRADES for example to Stylus RMX. This means that including the cost of the used discs, you can easily spend MORE than the cost of a new copy and STILL not be able to purchase the upgrade to RMX -- you must still spend the full amount. This policy is quite unfair to buyers but Spectrasonics refuses to flinch on this.

Overall:
If the upgrade policy were more fair, this product be an excellent stepping stone to Stylus RMX. But it's not. So given the style and flexibility limitations, for the cost it would be better take a look at other options.