Does Mavericks have a GUI for NFS mounts as in previous OS X versions?
A late answer, for posterity and the desperate searcher.

The GUI has been moved more or less to Directory Utility, which can be found in /Volumes/[name of your harddrive]/System/Library/CoreServices/Applications. Use -shift-G if you are lost to find your way. 

Open Directory Utility and click on the Directory Editor (third) icon.
Select "Mounts" from the dropdown menu Viewing (Node dropdown menu set to "/Local/Default") - if editing is locked, click the lock and enter an admin password.
Click the + icon in the lower left corner of the pane to start a new entry. Set "record name" to the server directory that you want connect to: [IP of server]:/[level1]/[level2] ….

Click "Save"

Click the + icon in the right half of the pane, to add (and save) the values for 
VFSLinkDir (full path to the mountpoint, that is, where the remote directory should be inserted), VFSOpts (I am using resvport,nolocks,locallocks,intr,soft,wsize=32768,rsize=32768,nosuid) and VFSType (nfs). The values for AppleMetaNodeLocation and GeneratedUID are generated automatically. 



Restart your computer.

Note added: After changing the NAS system I noticed that the above instructions worked with a Seagate BlackArmor NAS, but not with a WD MyCloud Mirror NAS. The WD NAS can be mounted as a NFS share under OS X 10.6.8 without problem. For a working connection with the WD NAS I used the following options: resvport,nolocks,locallocks,nosuid,rw,no_root_squash,no_subtree_check,soft,intr,rsize=8192,wsize=8192,timeo=900,retrans=3,proto=tcp,all_squash (I copied these from another site, maybe not all of them are required).