It appears the base model system can support a total of 8,000 320K MP3 files. I had a USB stick in it with about 11K, and it simply stopped reading after 8K. Pretty decent number of files for a stock unit, but I'm used to 40K+, so this is pretty meager for me. I think it's quite sufficient for most users, though. It took several minutes to play after first insertion, but only about 30 seconds after each new startup since then, which isn't horrible.
Sound-wise, I'd say it's pretty good for a stock setup. It's problems are more of omission: the lack of clarity, dynamics, detail, punch, bass power and extension, soundstaging, and imaging make for a highly sub-par system for my ears. However, the overall presentation isn't harsh or way off tonally, and it's not fatiguing or objectionable. It's just not very good in absolute terms for an audiophile. This is fine by me since I've always planned on replacing the entire thing anyway, and until I do so in a couple months, I can live with short-term it without too many complaints. I think most would like it just fine, but it's pretty lacking for mental patients like me. Also, I did check out the upgraded package system, and it was noticeably better than the base model. Still pretty severely lacking for my wants, though.