First off, let me say I hate to be the guy who is bitching about something awesome, and I'm not certain whether or not this is technically a rules questions but here we go anyway.
In my opinion for 200xp Wolf Scouts get to pay to be screwed. A dubious honor indeed. Now don't get me wrong, they get access to some pretty awesome stuff: unique talents, melee talents, and skills a lot earlier than otherwise. I like those things, I do. I promise.
The problem comes in when you look at what they get for the 200 xp, which amounts to a big bag of buggery and a nice pistol. You get an altered advance table which, sure, gives you some other stuff for cheap but changes something that was cheap into something that is very expensive. You also get to lose any and all special abilities, because switching out one skill for another and changing your advance table IS NOT A SPECIAL ABILITY, and really Wolf Scouts should get bolter mastery, I mean they do use bolters almost exclusively like any good tac-marines. You may like to bring up that you have the option of switching out to scout armor whenever you want... but since it was too sh*tty to have a requisition cost in the first place I don't see why you wouldn't have been able to do that at any point anyway, so that fits squarely in the not a bonus category. Also numerically a Raven Guard is a little more stealthy than a Wolf Scout...... even though the Raven Guard is in power armor and the Wolf Scout is in scout carapace...that means every single member of an entire chapter has the ability to be more stealthy in better armor than a stealth veteran in stealth armor, something about that just seems stupid to me. And to finish this out lets also not forget that by SPENDING 200 XP you lose the ability now and forever to by any talent that is at all related to Fellowship. So to review you spend xp to get the ability to spend more xp and get a nice shiny new pistol, but you also lose your potent special ability and can in no way be an awesome leader, so nice pistol and big bag of buggery.
To compare so that I don't sound like some whiner let's flip back a few pages and look at the Sanguinary Priest. For 500 xp you get access to an admittedly shorter list of goodies, but you get to keep your old special ability but you also get a new one, that among other things ups your Fellowship by 5 for the cost that buying up just fellowship alone would have done, oh and that new special ability is also totally badass, you also get two really good pieces of equipment AND access to two really awesome talents that few people can even get, and some hard to come by skills. Is there a downside to spending this 500 xp? Yes a very minor one that MIGHT cause your kill team to lose A TINY amount of Renown if you die and there are other Blood Angels in your Kill-team. So for 300 more Xp a Blood Angel gets an infinitely better deal than the Wolf Scout.
And just a little more proof, another Rank 1 only advanced Specialty which is totally rocking is the Tyrannic War Veteran, who for 1000xp gets a clip of really good special ammo as standard issue, round out their war gear so that they are good at either ranged or hand to hand combat, get a cool special ability without having to give up their starting one, and get access to some really good talents and skills, some of which are unique, and the ability to share the coolest of those talents with their buddies for the low cost of 1 Cohesion.... oh and they have NO DOWNSIDE. No downside and the possibility to be able to dodge hordes..... I mean.... come on, how do the Wolf Scouts even compare to that?
The short answer is: they don't.
I love the Space Wolves, and I understand that they have some pretty stand out stuff, and while I do not want them to be overpowered (it takes all the fun out of showing up all the other battle-brothers if you have an easier job of it) I do want to not get screwed over, and it really does seem like the Wolf Scouts are getting screwed over. That said I'm still playing one because I love the fluff and I love the attitude, but I wish it didn't feel like I'm being penalized for liking the lone wolf style character.
But as a fresh Rank 1 character with no extra xp when stacked up against a Sanguinary Priest or a Tyrannic War Vet, or hell to some degree even a kill marine or a Black Shield of the same level Wolf Scouts feel lacking. And even after you buy up both unique talents (2,500 xp later) if you are standing next to a Raven Guard he's still better at being stealthy than you are, and harder to kill, and has a special ability from his Specialty, which might make him better at doing pretty much anything you can.
It sucks is what I'm saying.