Check out this site for good NAS reviews:
http://www.smallnetbuilder.com/nas
There's quite a lot of semi-decent cheap NAS devices, but also the good ones have become quite a bit cheaper then before. Personally I prefer Qnap and Synology, had good experience with both of them
Performance: For large files even the cheaper devices are starting to have decent performance. You can really start to get close to saturating a gigabit network while moving a single multiple GB file at a time. When accessing multiple files at a time or moving small files things start to change, better NAS devices can be a lot faster, and having something like an Intel Atom processor will make a big difference. So what does he consider fast? 20MB/s or 100MB/s?
Features: Some devices are totally locked down, others give you root access and a packaging system allowing for adding just about anything you dream of as an add on (web applications, music streaming, version control etc). Some also now have cloud services and good tools for remote access.
I would not get a WD and especially not a basic Iomega, but they will probably both work. My previous was from Qnap and current from Synology, the nice thing is that generally they will allow you to do anything you suddenly need in the future, unlike previous WD/Buffalo NAS devices where you are locked down to whatever you had, and future operating systems (with new features) are only allowed on new devices. On the Synology I also have cloud support for my phone, nice remote access for contacting from work / vpn etc, so really everything you can ask for.
For remote access you really want to make sure he also configures the router and access properly. Only allow access to some specific service on the NAS, if possible use VPN, ensure authentication is encrypted, ensure he keeps the firmware of the NAS up to date (at least if there is security updates), limit access to some IP if possible etc.
Also look at backup features and notifications in case of problems. You don't want to run a NAS with important files without backup and you want to know as soon as there is a problem. RAID can be important if he always needs access to the device (even when a disk fails), but don't mix up RAID and backups (RAID is mainly to improve availability even when a disk has failed, backup is to recover from failure / user error).