People seem to like this unit a lot & I've run across used ones. I've noticed folks seem to be looking for sound cards. Are they discontinued and a problem to find? Will th unit work without them? Can patterns, fills, songs be programed into the unit? I've only used a Dr. Rythme and a Yamaha rythme machine so I'm very inexperienced but looking for some thing with top quality sounds and programability at a cost I can afford- Thanks

Tyler- The R8 will work fine without the sound cards: it has some very nice drum sounds internally, and the sound cards were just to give the user access to additional sounds. Note, however, that there are no "electronic" (i.e. TR-808, etc.) sounds in the unit itself - if you need that type of thing, you'll need to track down the sound cards. I THINK Roland US will sell them directly, but I'm not sure... the sounds in the unit were all I ever needed.
There are some things I really like about the R8, and some things I really hate. The pro's are the fact that there are 8 individual outputs in addition to the L&R stereo pairs, so if you're recording, you can spit all your snare drum sounds out of one output and lay some reverb on them. The fact that the pads are velocity-sensitive (if you set 'em that way) is nice, and I do a lot of my drum parts by hand. When you get one, you MUST sit down and carefully map out what drum sounds will equate to what MIDI note, and then map them. Trust me, if you do this once, you'll never want to do it again (it's numbingly tedious)but on the bright side, you've got it done right the first time.
The con's are that it IS difficult to program - maybe not as bad as some Yahaha's I've come across, but there are layers and layers of stuff you need to do, and it is not easy to master. I'd say I never use 90% of what the box can do, and I approach each drum programming session with a sense of dread... usually I write the tracks on my old faithful TR-707, spit 'em into the sequencer, and just use the R8 as a sound module, and to hand-play the whacky little percussion parts. You asked if patterns, fills, etc. can be programmed, and the answer is yes. There are about 40 Preset patterns in the machine which are quite nice (if a bit pedestrian, and can serve as a starting point for your own patterns. The unit has slots for 100 user patterns (which are built into songs, etc...) but in practice, with dense patterns you'll only have enough memory for about 75 or so. If you patterns are sparse (mine NEVER are!!) you can get up to the 100. There are no preset/programmed rolls, but you can always write dedicated roll patterns... basic Drumbo stuff.
I've had some BIG problems with the unit suddenly dumping it's memory when doing sysex dumps to my librarian, and have been fighting with Roland and my local music store for 2 years trying to straighten it out, but I can't honestly say that I'm sure it's Roland's fault.
I keep mine despite all this because the sounds ROCK. There are no effects, but some of the snares are exactly what I want in a Drumbo, versus the over-processed stuff in the newer machines. The R8 drums sound "honest", and I like that.
If the programming is difficult, it's only because there are so many features in the machine. Use what you want and ignore the rest.
Feel free to email me if you need more info... and I may be selling mine early next year, if you're interested - I'm not sure yet. It's a cash flow thing.