I have the R-09; got it just before the R-09HR came out. It sounds really good. The HR adds 24/96 capability, which is better than CD quality. You might consider whether you need that if recording acoustic guitar, as the instrument doesn't get anywhere near the limits of frequency response and dynamic range. The R-09 could be as much as $100 cheaper now, and you could use the cash to buy a nice mic.
Speaking of mics, the built-in ones on the R-09 aren't bad at all. If you place the unit the way you would a mic, the result is not far off what you'd get with a nice condenser. It's an audible difference, but it's not big.
For multi-track, I have a Roland VS-1680. It's old school now, but was appealing back when I got it because it doesn't crash. Even has mix automation, though it's not what you'd call intuitive.
For practicing and developing ideas, I've been using a Digitech JamMan. This is a looping pedal on steroids. With a 2GB CF card, it will record a six hour loop! It has 99 memory locations, into which you can record loops. You can save loops, layer sound on sound, change tempo and so on. I use it for electric guitar, but it has a mic level input, so you could use it with acoustic if you were so inclined. I like practicing my improv by laying down a groove and then soloing over it. We even used the thing live at OFG's party to lay down the groove for a little jam at the beginning of the set.
musician thread.
Hooli no like that 
