Hi,
Regarding your question regarding the Tyros4

1. It does not have an arpeggiator

2. Not really,pretty difficult to follow.Pretty much the same as all other brands.

3. There seem to be an issue with the Audio Recorder,but doesn't seem to apply to all Tyros4s

IE.When recording the disk drive will stop operating and a disk full warning is displayed.
Which in most cases have not been cured by the fitting of a new disk.

The initial saving and memory issues have been address by an OS update.It now seems most issues reported turn out to be user operational Errors.

I certainly would not part with mine and have no issue since the update.Hope this will help.

Gilbert.