Ah. My misunderstanding. I thought you were trying to argue that all of the services are broken and curious as to what you should use.
The problem, in the most simplistic terms is this:
We support AFP, CIFS, and NFS protocols per the afpd, sambad, and nfsd daemons. Those are maintained for many *BSD and Linux OSes as well as others. If there's a bug that is for sure not a user-error problem the fact is either everyone else is experiencing the error or the error is with FreeNAS' implementation. Both of those are likely to be well documented so you should be able to validate the problem as well as some kind of hacky solution to get by. The client having a problem does happen, but is very much in the minority of cases.
Once you've ruled those three out the remaining options are pretty much all user-error. Be it improper client setup, improper networking, etc. When it comes to troubleshooting the issues you are very much on your own at this point. We provide the protocol and you get to use it. If and when things don't work the number of places that can have problems is quite high. We've seen everything from bad NICs on the server and/or client to bad RAM on a client to someone that has "tuned" their OS for higher speeds with windows registry hacks that break things they didn't know about. You name it we've seen it. The best we can do is tell you that it works for us and that your issue is not too well documented and let you try to figure out why your client or network doesn't want to work. Once we've ruled out the server, trying to help you is darn near impossible without one-on-one care. iXsystems does offer that kind of thing on-contract. But most of us here can't spend that kind of money on it.
As an non-XBMC user I'm not sure if you are using NFS because you must or because you want to. I do see that NFS is supposed to be faster. I'm presuming that its referring to CPU usage of NFS vs CIFS and not throughput because CIFS easily saturates Gigabit with modest hardware. Plex doesn't quite work the same and I use Plex with a linux server that maps my FreeNAS box via CIFS. It works great and I've never had a problem with it. I could easily have done NFS and I'm sure it would have worked just as well.
NFS isn't the major sharehold for *nix because there's too many people that need to run OSes that don't do NFS- mainly Windows products. Yes, Windows has NFS support if you have a version that supports it, but the performance is very lacking. NFS is often used for backbone activities like ESXi and such, but for desktops I'd say it's probably in the minority in terms of % used. Since you aren't supposed to share the same files with multiple protocols your options usually go from choosing one of the three to CIFS in very short order.
As for you noticing that OSX and raspbmc exhibiting the same behavior, your guess is as good as mine. OSX is a PITA around here. There aren't many Apple users here and the ones that are usually have a problem. With no hardcore Apple base here getting help with Apple products is almost impossible.
You won't find very many XBMC users around here. Especially since Plex has a plugin for FreeNAS that is dead-simple to install. Many users around here that have used XBMC in the past are using Plex now because it's available and they can do everything on the server without having to jack around with sharing stuff for XBMC.
My avatar wasn't picked by me. It was picked by the CTO of the FreeNAS project. ;) It is somewhat related to my job around here as I've had to be the bearer of bad news and I'm pretty up-front with telling people to RTFM if they ask some question that is so stupid they need to be pointed to the manual. If my avatar puts you off you are welcome to not use the forums. I've been in other forums that have far far more offensive things than a dog with teeth. We've had to tone down people's profile picts in the past.. women with almost no clothing, cusswords, drug paraphernalia, and what-not. You can always drop in IRC and ask your question there.
I'm not sure how much you've worked in BSD or Linux forums, but they can be pretty hardcore. They expect a certain level of knowledge and they often provide lots of documentation for you to read. They don't expect you to be a pro, but they do expect you to at least have the basics. We get people confused as to how to do things like set an IP address and ask what an IP address is. The FreeBSD forums have been known to ban people outright for bad grammar, punctuation, spelling, not including all the stuff that forums expect like software version, error codes, outputs of some commands, etc. You want to see people with teeth go to the FreeBSD forums. I don't even post there its so strict.
Anyway, to wrap this up the only thing I can personally say is "good luck". NFS works for me and I'm not sure I've seen someone complain of NFS shares that always show 0 bytes.
Just out of curiosity have you looked at
http://doc.freenas.org/index.php/Unix_(NFS)_Share ? You do know that NFS shares can't cross filesystem boundaries and datasets ARE filesystem boundaries.
