I have a bit of experience with the longhaired Weimaraner!
They are exactly the same as the shortcoated Weimaraner just with a different hairdo.
I have had 4 Weimaraners, two shorthairs and two long hairs, two males and two females.
I have worked them all successfully to one degree or another; worked one SH and one LH in "ticket" in Working Trials. My current longhair bitch (retired) is the most titled dog of any breed in the UK ever.
Her full title is Fursdon Twylyte Tramontano K9MS2 AD BH FH1 FH2 CDex UDex WDex TDex. She has won a ticket in Working Trials, holds a Working Gundog Certificate, competed successfully in KC Agility, is a registered PAT dog, Gold Good Citizen's Test and today obtained an "excellent" in a character assessment (along with my "other" german, the GSD).
I have judged HV and HWV in Working Trials and I prefer the HWV in my limited experience I have found them to be "stronger" than the shorts. One of the reasons I did not have a HV was that I thought I would be too "strong" for them.
Longhaired Weimaraners are not judged separately in the show ring as they are on the continent. One of the reasons for this is because they are numerically small; it would be a good year (depending upon your point of view) where LH births reached 30. This is because many people do not like them, although IME when manning gundog tents, Discover Dogs etc it is the LH that attracts all the attention and many people prefer their look.
I beleive it is more likely for mixed litters to increase now with the advent of the anti docking laws as it is extremely difficult to tell the shorts from the longs in a litter in time for them to be docked. Longhairs have never been docked (although the standard did say you could tip the tail).
The only country that does not recognise Longhairs is USA.
Unlike the GLP, GSP and GWP or HV and HWV they are not a separate breed, just a different coat variant.
Weimaraners can do anything you want them to do, it is not any lack in the breed that stops them, rather their owners IME!