I've got an NV+ too. Had it about a year. Works like a charm. The people at Infrant (now Netgear) have been pretty good at updating the linux based software it runs, in particular to support OS X (e.g. adding the Time Machine support, faster sharing using AFP etc.) and new drives (e.g. a firmware update was needed to support 1TB disks when they came out). There are pretty well informed / busy discussion forums for the device too at http://www.readynas.com/forum - including one dedicate to OS X users / issues.
Only challenge I've had (and others too) is getting anything approaching fast network transfers to work well. The device has G-ethernet and supports Jumbo frames etc, but real-world transfer speeds to Macs seem to max out for most people well below 30Mb/s. There is also a big performance hit copying many small files (e.g. contents of a MailDir directory) - the system is optimised very much for large media style files.
But these are minor issues - it is a good stable product. Saving up for a set of 1Tbyte drives... :)
Review: Infrant NAS NV+