The R09 internal mics are just fine for what you're looking to do. Hassling with an external mic would make the process less enjoyable if you're just trying to get soundscapes. Last year I went to Disney World and brought along my old MD wth an external mic, and I found that the self noise on my hand held mic really annoyed me. I had to hold perfectly still or else all I would hear would be the sound of the mic rubbing up against something.
I bought my R09 when my PCM-M1 DAT recorder died this summer. I liked that there were no moving parts (the death of my M1), the 24bit recording ability and the drag and drop ease of data transfer. I don't even really burn discs anymore, I archive the 24bits, upload Archive friendly artists to the Archive.org, and make a personal copy for my iPod. It's wonderful.
Once I found out how good the internal mics were for on-the-fly recordings, I started taking it around more often. I brought it to a travel convention earlier this year, and captured a Fijian band playing a traditional song called "Bula Malaya". I wouldn't have bothered bringing my MD, but the R09 did a great job recording the song.
http://www.scubajeremy.net/Fiji_Singers_Compressed.mp3I did compress the track to balance the clapping vs the guitar work, but the track still sounds pretty good. The R09 is excellent in terms of self noise. Just holding the unit will not cause noise on the internal microphones.
For what you're looking for, I'd say the F09 is an excellent choice. Go with a Transcend 4GB card, and you'll have over 4 hours of 24bit 48 Khz. At 24bit 16 Khz, you'll have over 4 hours, and I think you can get just over 5 hours at CD quality, 16bit, 44.1Khz. If you start to step down to MP3, you can get more time, but I would reccomend getting another SD card. You can get the Transcend 4GB card for under $100, probably even under $75, it's been a while since I've looked.
I hope I've helped. I know I'm bringing my R09 when I travel to Argentina next summer. I can't wait!